Add missing container-parameters to Data

[fflaten]

PR Summary

Pester containers may use parameters to support data-driven test generation.

This scenario currently has the following limitations:

• Default values for parameters are available as variables in Discovery, but not in Run (test execution) unless passed using tricks like Describe 'd1' -ForEach { myparam = $myparam}. This makes debugging harder since Debug Tests in VSCode doesn't allow the user to provide -Data ... for the container (file).
• Default values are also not available in *All/*Each setup-blocks placed outside any Describe/Context-blocks. The Describe -ForEach ..-workaround above does not work for these root-scoped setup-blocks.
• Discovery and Run are inconsistent when using aliases for script parameters. Given a container with parameter "MyParam" which has a alias of "MyAlias". When invoked with New-PesterContainer ... -Data @{ MyAlias = 123 }:
  • In Discovery: $MyParam would be 123 and $MyAlias would not exist. This is default PowerShell-behavior.
  • In Run: $MyParam would not exist and $MyAlias would be 123. This is because Pester adds uses the provided -Data directly during Run.

This PR adds logic to detect container-parameters not defined by the user at runtime and automatically adds them to Data for the Root-block of the container. New behavior:

• Script-parameters are always available as variables in Discovery and Run. Has default value (null or value set in Param-block) if not provided by the user.
• Default values are available in root-scoped setup blocks.
• $MyParam (see example above) is also defined in Run like it is in Discovery to be more consistent and similar to normal PowerShell-function/script behavior.

Fix #1980

PR Checklist

• PR has meaningful title
• Summary describes changes
• PR is ready to be merged
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• Tests are added/update (if required)
• Documentation is updated/added (if required)

[fflaten]

I think this is ready for review. Wondered if it should have some tests when using InModuleScope .. -Parameters ... outside the blocks etc, but I'm not really sure how that's supposed to work even before this. Couldn't really pass any Data to run-phase, but that's probably user-error. I try to stay away from InModuleScope outside *All/*Each/It.

[nohwnd]

I am not sure how that should work either. 😬