Support mocking and execution in manifest modules

[fflaten]

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PR Summary

Adds support for manifest module to Mock, Should -Invoke and InModuleScope.

Fix #1456 Fix #933

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[fflaten]

Stumbled into an issue with force-importing manifest module with nested module, https://gist.github.com/fflaten/0df7afe3c2a781e2de29aeb55df0b8ff

This causes alias and mock to be placed in old import of a nested module while public function will execute in new and as a result not find the mock.

Workaround: Always remove manifest-module before re-importing. Ex.

BeforeAll {
    Get-Module ManifestModule -ErrorAction SilentlyContinue | Remove-Module
    Import-Module ManifestModule.psd1`
}

I believe this is intentional to avoid overwriting a module that was already imported in the session, while the manifest module will call the updated one (which we can see is updated in (Get-Module ManifestModule).NestedModules)