Publish-PSResource: honor ExternalModuleDependencies from PrivateData.PSData during dependency validation

[PrzemyslawKlys]

Summary

Fix Publish-PSResource dependency validation so ExternalModuleDependencies are respected for module manifests when declared under PrivateData.PSData.

Problem

Publish-PSResource excluded external dependencies only when ExternalModuleDependencies was present at the top level of parsed metadata.
For module manifests, this value is typically stored under PrivateData.PSData.ExternalModuleDependencies, so the dependency check could still fail and incorrectly require
-SkipDependenciesCheck.

Root Cause

ParseRequiredModules() only looked at:

• parsedMetadataHash["ExternalModuleDependencies"]

and did not also inspect:

• parsedMetadataHash["PrivateData"]["PSData"]["ExternalModuleDependencies"]

Also, dependency key matching was case-sensitive.

Changes

• Updated ParseRequiredModules() in src/code/PublishHelper.cs to:
  • read external module dependencies from both top-level metadata and PrivateData.PSData
  • use robust nested hashtable extraction
  • normalize matching via case-insensitive dependency map keys
• Added regression test in:
  • test/PublishPSResourceTests/PublishPSResource.Tests.ps1
  • test name: Publish a module with ExternalModuleDependencies that are not published

Validation

• Added publish regression test covering module manifest external dependency behavior.

[PrzemyslawKlys]

I've updated PR with additional test proving this is actually needed. Right now if you publish something with External Dependencies in place - you won't be able to download it without issues. This seems critical to me.