[vs17.13] Fix SdkResult Evalution when ProjectRootElement is null

[surayya-MS]

Fixes #11550

Context

This is a regression caused by changes in MSBuildSdkResolver that were introduced in dotnet/sdk#45364. Specifically by adding 2 new properties.
This results in hitting the path that was not hit before - handling properties and items of SdkResult:

msbuild/src/Build/Evaluation/Evaluator.cs

Lines 1867 to 1875 in 6aeb262

	if ((sdkResult.PropertiesToAdd?.Any() == true) ||
	(sdkResult.ItemsToAdd?.Any() == true))
	{
	projectList ??= new List<ProjectRootElement>();
	// Inserting at the beginning will mean that the properties or items from the SdkResult will be evaluated before
	// any projects from paths returned by the SDK Resolver.
	projectList.Insert(0, CreateProjectForSdkResult(sdkResult));
	}

When Project is created from XmlReader and not from ProjectRootElement, it results in null ProjectRootElement during Evaluation. Which results in internal exception like InternalErrorException: MSB0001: Internal MSBuild Error: .SdkResolver.1981936763.proj unexpectedly not a rooted path here:

msbuild/src/Build/Evaluation/Evaluator.cs

Line 1928 in 6aeb262

string projectPath = $"{_projectRootElement.FullPath}.SdkResolver.{propertiesAndItemsHash}.proj";

Above created project path is just .SdkResolver.1981936763.proj with no directory. Later exception is thrown here because of it:

msbuild/src/Build/Evaluation/ProjectRootElementCache.cs

Line 262 in 9e51a07

ErrorUtilities.VerifyThrowInternalRooted(projectFile);

or here if you use SimpleProjectRootElementCache:

msbuild/src/Build/Evaluation/SimpleProjectRootElementCache.cs

Line 43 in 9e51a07

ErrorUtilities.VerifyThrowInternalRooted(projectFile);

Changes Made

Changed the projet path that is created for SdkResult properties and items - if there is no ProjectRootElement then generate name like {Guid}.SdkResolver.{propertiesAndItemsHash}.proj in the current directory.

Testing

Added test. Tested manually as well

Notes

[rainersigwald]

Change looks pretty good to me but at this point I think we should fix in 17.14. If we want to service 17.13 we need to put together the evidence in support of that.

[surayya-MS]

Closing this PR because we want to target 17.14 #11636