Analyzers prototyping - properly inject bootstrap location into tests

[JanKrivanek]

Context

#9380

Goals

Tha sample unit test works properly regardless of the curent target FW and configuration and regardless of how/where we place our bootstrap binaries.
Current code:

msbuild/src/UnitTests.Shared/RunnerUtilities.cs

Lines 42 to 50 in 9fb9f56

	// TODO: use proper way of passing the bootsrtrap location: https://github.com/dotnet/msbuild/issues/9729
	string basePath = PathToCurrentlyRunningMsBuildExe.Substring(0, PathToCurrentlyRunningMsBuildExe.IndexOf(@"artifacts\bin", StringComparison.InvariantCultureIgnoreCase));
	#if NET
	string pathToExecutable = EnvironmentProvider.GetDotnetExePath();
	msbuildParameters = Path.Combine(basePath, @"artifacts\bin\bootstrap\net8.0\MSBuild\msbuild.dll") + " " + msbuildParameters;
	#else
	string pathToExecutable =
	Path.Combine(basePath, @"artifacts\bin\bootstrap\net472\MSBuild\Current\Bin\amd64\msbuild.exe");
	#endif

Proper way - the bootstrap location from the build script is passed via property into the compiled test binary and hence proper location is used

[JanKrivanek]

Fixed by #9733