Use MSBuild Locator's AppDomainManager

[sharwell]

Starting with #36113, AnalyzerRunner uses the AppDomainManager from SourceBrowser to work around microsoft/MSBuildLocator#16. Once MSBuild Locator ships its own copy of a custom AppDomainManager, the changes in commit fbc4b38 should be updated to use that version instead, and the references to SourceBrowser removed from dotnet/roslyn.

[CyrusNajmabadi]

Closing out as speculative. If we need to do this, we should just have a milestone and do it.