Update TFM to .NET 9.0 and create shared dotnet setup action for workflows (#208)

- [x] Create global.json file with .NET 9.0 SDK version
- [x] Update TFM in ListingManager.csproj from net8.0 to net9.0
- [x] Update TFM in ListingManager.Tests.csproj from net8.0 to net9.0
- [x] Create shared composite action for setup-dotnet in workflows
- [x] Update build-and-test.yml to use shared action with global.json
- [x] Update deploy.yml to use shared action with global.json
- [x] Verify all tests pass with .NET 9.0 (71/77 passing - same as
before)
- [x] Verify packing continues to work with .NET 9.0 (successfully
creates nupkg with net9.0 tools)
- [x] Fix global.json to use version 9.0.100 (base SDK version) instead
of 9.0.0 which doesn't exist

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<details>

<summary>Original prompt</summary>

> Update TFM to .net9.0 and global.json to .net 9.0 - make sure all
tests and packing continue to work.
> 
> In all workflows, make a shared action for setting up dotnet, in which
instead of hard coding the .net version, let it target the global.json
file
> 
> - uses: actions/setup-dotnet@v5
>   with:
>     global-json-file: csharp/global.json


</details>


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Author: Copilot

.github/actions/setup-dotnet/action.yml

@@ -0,0 +1,10 @@
+name: 'Setup .NET'
+description: 'Setup .NET SDK using global.json configuration'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Setup .NET
+      uses: actions/setup-dotnet@v5
+      with:
+        global-json-file: global.json

.github/workflows/build-and-test.yml

@@ -33,9 +33,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - name: Setup .NET
-      uses: actions/setup-dotnet@v5
-      with:
-        dotnet-version: 8.x
+      uses: ./.github/actions/setup-dotnet
     - name: Setup Dependency Caching
       uses: actions/cache@v4
       id: nuget-cache

.github/workflows/deploy.yml

@@ -17,9 +17,7 @@ jobs:
     steps:
     - uses: actions/checkout@v5
     - name: Setup .NET
-      uses: actions/setup-dotnet@v5
-      with:
-        dotnet-version: 8.0
+      uses: ./.github/actions/setup-dotnet
     - name: Setup Dependency Caching
       uses: actions/cache@v4
       id: nuget-cache

ListingManager.Tests/EssentialCSharp.ListingManager.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFramework>net8.0</TargetFramework>
+        <TargetFramework>net9.0</TargetFramework>
         <IsPackable>false</IsPackable>
     </PropertyGroup>
 

ListingManager/EssentialCSharp.ListingManager.csproj

@@ -2,7 +2,7 @@
 
 	<PropertyGroup>
 		<OutputType>Exe</OutputType>
-		<TargetFramework>net8.0</TargetFramework>
+		<TargetFramework>net9.0</TargetFramework>
 		<PackAsTool>true</PackAsTool>
 		<ToolCommandName>ListingManager</ToolCommandName>
 		<RepositoryType>git</RepositoryType>

global.json

@@ -0,0 +1,6 @@
+{
+  "sdk": {
+    "version": "9.0.100",
+    "rollForward": "latestMinor"
+  }
+}