Analyzer support for Unforked Null Safe SDK

[stereotype441]

Everything needed to be able to safely analyze legacy projects once the SDK is unforked. Includes language versioning functionality.

[franklinyow]

Are we ready to close this Epic?

[stereotype441]

Are we ready to close this Epic?

Yes, I think so. It's possible that more issues will be disovered when we try to actually land the un-fork CL, but if they do we can address them as they arise.