Versioning: Redirect Rule and Commit Build ID API

[carlydf]

What changed?

Implemented insert / replace / delete redirect rule API, and CommitBuildID

Why?

For use in worker versioning

How did you test it?

Cycle test has a unit test. Further tests coming in next PR.

Potential risks

Nothing, this is a new feature.

Is hotfix candidate?

No.

Questions / To do's

• Should we update the comment on the API proto to state the requirement that the rule's TargetBuildId not be in an existing version set? If so, I can make the update here
• When CommitBuildId says it "removes the ramp of any incoming redirect rules to this Build ID.", I'm not clear on that since only assignment rules have ramp.