UpgradeMSBuildWorkspaceAnalyzer tests doesn't match real behavior

[Youssef1313]

roslyn-analyzers/src/Microsoft.CodeAnalysis.Analyzers/Core/UpgradeMSBuildWorkspaceAnalyzer.cs

Lines 37 to 40 in f361553

	protected UpgradeMSBuildWorkspaceAnalyzer(bool performAssemblyChecks)
	{
	_performAssemblyChecks = performAssemblyChecks;
	}

This is always true in production code:

roslyn-analyzers/src/Microsoft.CodeAnalysis.Analyzers/CSharp/CSharpUpgradeMSBuildWorkspaceAnalyzer.cs

Lines 18 to 21 in f361553

	public CSharpUpgradeMSBuildWorkspaceAnalyzer()
	: this(performAssemblyChecks: true)
	{
	}

and always false in unit tests:

roslyn-analyzers/src/Microsoft.CodeAnalysis.Analyzers/UnitTests/UpgradeMSBuildWorkspaceAnalyzerTests.cs

Lines 123 to 129 in f361553

	internal class TestCSharpUpgradeMSBuildWorkspaceAnalyzer : CSharpUpgradeMSBuildWorkspaceAnalyzer
	{
	public TestCSharpUpgradeMSBuildWorkspaceAnalyzer()
	: base(performAssemblyChecks: false)
	{
	}
	}

Something is wrong here. @mavasani I'd like to clean this up, but want to understand more the expected behavior from this analyzer and some history and what problem it is trying to solve.

[Youssef1313]

I attempted to fix this in #6324. But none of the tests produce a diagnostic when executed against the "real" analyzer used in production.

[Youssef1313]

I think I was able to correct the tests per https://gist.github.com/jmarolf/49173eb81f7bd26a2709087c5769c727 (thanks @jmarolf for this gist).