feat(server): rpc rescue threadRun

[coltmcnealy-lh]

Allows rescuing a failed ThreadRun. Currently, only entrypiont ThreadRun's may be rescued.

[coltmcnealy-lh]

I'm marking this as "Ready for Review." The current limitations are:

• We only support rescuing the "Parent" ThreadRun.
• We don't support reviving halted Child ThreadRuns after rescuing the parent.

Both issues will be addressed in a follow-up PR. I am separating them in an attempt to keep the code easier to understand.

You'll also notice I'm not doing throw new LHApiException but rather passing around a grpc Optional<Status> flag. The reason for this is because at one point we will have the ability to Bulk Rescue ThreadRun's by looking for WfRun's that failed due to a certain TaskRun failing. It won't make sense to throw an LHApiException in that case because there won't be a waiting client to accept it.