Remove Mock fallthrough

[nohwnd]

PR Summary

Mock no longer falls through to the original command when no behavior matches. It throws instead. Fix #2178.

Invoke-Pester -Container (New-PesterContainer -ScriptBlock {
    Describe "a" {
        It "b" {
            function FunctionUnderTest ($param1) {}
            Mock FunctionUnderTest { "fake" } -ParameterFilter { $param1 -eq "test" }
            FunctionUnderTest -param1 "other"
        }
    }
})

[-] b
  RuntimeException: No mock for command 'FunctionUnderTest' matched the call: none of
  the parameter filters matched, and there is no default mock to fall back to. Add a
  default mock (e.g. `Mock FunctionUnderTest { ... }`) or adjust an existing -ParameterFilter.

  The following parameter filters were evaluated and did not match:
      mock filter: {  $param1 -eq "test"  } without any parameters

A separate message points at the bootstrap-leak case (outer Mock leaking into a nested
Invoke-Pester whose own mock table is empty) since there are no filters to show in that path.

[nohwnd]

The error message is pretty terrible. We will see it only when there is no default behavior, so there must be at least 1 paramtrized mock.

I tried to show what we evaluated in order to reach that point where no filter matched. but the wording needs to be better, and well as the formatting of the invoked filters I think.

But then we should be able to re-use similar thing for Should -Invoke to show the history of execution, when failing should Invoke. To show the performed invocations.

[nohwnd]

Removed the orphan-bootstrap fallthrough entirely at 349ed05 — Invoke-MockInternal no longer ever invokes the original command. The NoBehaviors branch and its 30+ lines of original-command setup are gone.

What happens now in the leaked-bootstrap case (outer Mock Get-Date {1} + nested Invoke-Pester where the inner run calls Get-Date without its own mock): throws with a clear, actionable message:

No mock for command 'Get-Date' is defined in this scope, but the bootstrap is active (typically a Mock from an outer scope leaked into a nested Invoke-Pester run). Add a Mock for 'Get-Date' in this scope, or restructure the test so the outer Mock does not leak.

The pre-existing nested-Pester test (Describe 'Mocking with nested Pester runs') is updated to assert the throw instead of expecting silent fallthrough. The inner local mock works test still passes.

Also fixed the two PSScriptAnalyzer warnings: ForEach-Object calls in Mock.ps1 now go through & $SafeCommands['ForEach-Object'].

229/229 in Mock.Tests, 2183/0 full suite green on PS 7.6.