Disable EnsureEnvironmentExitDoesntHang on .NET Framework (dotnet#125912)

`ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang` fails on .NET
Framework because `System.Console.ControlCHooker.Unhook()` throws
`IOException: The parameter is incorrect` during process finalization,
causing an unhandled exception (exit code -532462766 /
EXCEPTION_COMPLUS). This is a known .NET Framework shutdown limitation.

## Changes

- Added `[SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework,
"NET Framework shutdown issue")]` to `EnsureEnvironmentExitDoesntHang` —
consistent with the existing skip on the related
`EnsureEnvironmentExitCode` test
- Simplified the test body: removed the now-dead `expectedExitCode =
PlatformDetection.IsNetFramework ? 0 : 125` conditional, inlining `125`
directly

> [!NOTE]
> This PR description was generated with AI assistance (GitHub Copilot).

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<details>

<summary>Original prompt</summary>


----

*This section details on the original issue you should resolve*


<issue_title>Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang
fails on .NET Framework</issue_title>
<issue_description>## Build Information
Build:
https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1143743
Build error leg or test failing:
Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang
Pull request: dotnet#119515

Console excerpt:
```
    Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang [FAIL]
      Microsoft.DotNet.RemoteExecutor.RemoteExecutionException : Exit code was -532462766 but it should have been 0
      Stack Trace:
        /_/src/arcade/src/Microsoft.DotNet.RemoteExecutor/src/RemoteInvokeHandle.cs(242,0): at Microsoft.DotNet.RemoteExecutor.RemoteInvokeHandle.Dispose(Boolean disposing)
        /_/src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/ConsoleLifetimeExitTests.cs(223,0): at Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang()
```

-532462766 corresponds with EXCEPTION_COMPLUS.

```json
{
  "ErrorMessage": "ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang [FAIL]",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}
```

<!-- Known issue validation start -->
 ### Known issue validation
**Build: 🔎**
https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743
**Error message validated:**
`[Microsoft\.DotNet\.RemoteExecutor\.RemoteExecutionException : Exit
code was -532462766 but it should have been
0.*EnsureEnvironmentExitDoesntHang()`]
**Result validation:** ❌ Known issue did not match with the provided
build.
**Validation performed at:** 9/10/2025 6:12:29 PM UTC
<!-- Known issue validation end -->
<!-- Known issue validation start -->
 ### Known issue validation
**Build: 🔎**
https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743
**Error message validated:**
`[Microsoft.DotNet.RemoteExecutor.RemoteExecutionException : Exit code
was -532462766 but it should have been 0`]
**Result validation:** ✅ Known issue matched with the
provided build.
**Validation performed at:** 9/10/2025 7:05:39 PM UTC
<!-- Known issue validation end -->
<!--Known issue error report start -->

### Report

|Build|Definition|Test|Pull Request|
|---|---|---|---|

|[1143743](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743)|dotnet/runtime|[Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743&view=ms.vss-test-web.build-test-results-tab&runId=31540798&resultId=103521)|dotnet/runtime#119515|
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|1|1|1|
<!--Known issue error report end -->
<!-- Known issue validation start -->
 ### Known issue validation
**Build: 🔎**
https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743
**Error message validated:** `[at System.Console.ControlCHooker.Unhook`]
**Result validation:** ✅ Known issue matched with the
provided build.
**Validation performed at:** 9/10/2025 7:07:38 PM UTC
<!-- Known issue validation end -->
<!--Known issue error report start -->

### Report

|Build|Definition|Test|Pull Request|
|---|---|---|---|

|[1143743](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743)|dotnet/runtime|[Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1143743&view=ms.vss-test-web.build-test-results-tab&runId=31540798&resultId=103521)|dotnet/runtime#119515|
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|1|1|1|
<!--Known issue error report end -->
<!--Known issue error report start -->

### Report

|Build|Definition|Test|Pull Request|
|---|---|---|---|

|[1174378](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1174378)|dotnet/runtime|[Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1174378&view=ms.vss-test-web.build-test-results-tab&runId=32501172&resultId=104197)||

|[1170349](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1170349)|dotnet/runtime|[Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitTests.EnsureEnvironmentExitDoesntHang](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1170349&view=ms.vss-test-web.build-test-results-tab&runId=32385630&resultId=103595)|dotnet/runtime#120603|

|[1169444](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1169444)|dotnet/runtime|[Microsoft.Extensions.Hosting.Tests.ConsoleLifetimeExitT...

</details>



<!-- START COPILOT CODING AGENT SUFFIX -->

- Fixes dotnet#119545

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: danmoseley <6385855+danmoseley@users.noreply.github.com>

Author: Copilot

src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/ConsoleLifetimeExitTests.cs

@@ -205,11 +205,9 @@ await Task.Run(() =>
         /// Tests that calling Environment.Exit from the "main" thread doesn't hang the process forever.
         /// </summary>
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, "NET Framework shutdown issue")]
         public void EnsureEnvironmentExitDoesntHang()
         {
-            // SIGTERM is only handled on net6.0+, so the workaround to "clobber" the exit code is still in place on .NET Framework
-            int expectedExitCode = PlatformDetection.IsNetFramework ? 0 : 125;
-
             using var remoteHandle = RemoteExecutor.Invoke(async () =>
             {
                 await Host.CreateDefaultBuilder()
@@ -219,7 +217,7 @@ await Host.CreateDefaultBuilder()
                         services.AddHostedService<EnsureEnvironmentExitDoesntHangWorker>();
                     })
                     .RunConsoleAsync();
-            }, new RemoteInvokeOptions() { TimeOut = 30_000, ExpectedExitCode = expectedExitCode }); // give a 30 second time out, so if this does hang, it doesn't hang for the full timeout
+            }, new RemoteInvokeOptions() { TimeOut = 30_000, ExpectedExitCode = 125 }); // give a 30 second time out, so if this does hang, it doesn't hang for the full timeout
         }
 
         private class EnsureEnvironmentExitDoesntHangWorker : BackgroundService