Add support for adapted resource manifests for PowerShell 7 adapter

[SteveL-MSFT]

PR Summary

Add support for PowerShell 7 adapted resource manifests.
Note that WindowsPowerShell isn't supported because it relies on PSDSC module using Get-DscResource which only supports finding resources installed for the system.

Also some general fixes found during debugging where splitting $env:PSModulePath could have empty segments which broke the code since it was now passing $null to a cmdlet.

To keep the existing code working, the main change in the adapter is when resourcePath is supplied to import that module and then subsequent code that creates internal structure with the DSC resource tries to use the loaded module first before falling back to existing discovery code. This also means that for an adapted resource manifest, it entirely skips the legacy discovery path so it's much faster.

While testing the change, I noticed that currently there is no way to pass the resource version if specified to the adapter in single mode, created #1414 to handle later, but not blocking.

PR Context

Fix #1412

[Copilot]

Pull request overview

Adds adapted resource manifest support for the PowerShell 7 adapter by allowing the engine to pass a resourcePath into the adapter, importing the module directly, and short-circuiting legacy discovery for faster adapted-manifest operations. This also wires resourcePathArg through the adapter manifests and adds test resources + Pester coverage for the new behavior (including the WinPS “not supported” path).

Changes:

• Add -ResourcePath handling to the PowerShell adapter entrypoint and pass it through adapter manifests.
• Enhance module/resource discovery to consider already-imported modules and add a fast-path cache refresh for imported DSC modules.
• Add adapted-manifest test resources and Pester tests to validate list/get behavior and WinPS unsupported behavior.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
adapters/powershell/psDscAdapter/psDscAdapter.psm1	Adds imported-module inclusion in discovery and a fast-path in Invoke-DscCacheRefresh; adjusts module import usage for type lookup.
adapters/powershell/psDscAdapter/powershell.resource.ps1	Adds ResourcePath parameter, imports the specified module for adapted manifests, and throws on WinPS.
adapters/powershell/PowerShell_adapter.dsc.resource.json	Adds resourcePathArg wiring for get/set/test/export operations.
adapters/powershell/WindowsPowerShell_adapter.dsc.resource.json	Adds resourcePathArg wiring so WinPS adapter can detect adapted manifests and throw.
adapters/powershell/Tests/PSAdaptedTestClassResource.psm1	New class-based DSC test resources for adapted manifests.
adapters/powershell/Tests/PSAdaptedTestClassResource.psd1	New test module manifest exporting DSC resources and capabilities.
adapters/powershell/Tests/PSAdaptedTestClassResource.dsc.adaptedResource.json	New adapted resource manifest for PS7 adapter scenario.
adapters/powershell/Tests/WinPSAdaptedTestClassResource.dsc.adaptedResource.json	New adapted resource manifest targeting WinPS adapter (unsupported).
adapters/powershell/Tests/PSAdapted.tests.ps1	New Pester tests validating adapted-manifest discovery and operations.
adapters/powershell/Tests/.project.data.json	Ensures test artifacts are copied into the test environment.

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