simplify private asset package references

[adamralph]

What issue does this PR address?

Redundant private asset package reference complexity.

[Copilot]

Pull Request Overview

This PR simplifies MSBuild package references by reducing verbose XML configurations for private asset packages. The changes streamline package reference declarations while maintaining the same functionality.

• Removed verbose multi-line PrivateAssets and IncludeAssets XML elements
• Converted to inline attribute syntax where PrivateAssets="all" is needed
• Simplified test-only package references to basic self-closing tags

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
test.props	Simplified coverlet.collector and xunit.runner.visualstudio package references to basic declarations
src.props	Converted MinVer package reference from verbose XML to inline PrivateAssets attribute

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