In an effort to begin moving to "owner" as the new terminology for a

review request instead of "submitter," this change renames the condition

choice names and values to use "owner" instead. This will break any

conditions on the Submitter field filed during the beta, but it's a

worthwhile breakage in order to avoid maintaining legacy keys going

forward in conditions.
ReviewRequest also gained an owner property that aliases

submitter, which is used in the condition choices and will be used in

future changes. ReviewRequestDraft has such an attribute already, so

this provides a good counterpart, allowing callers to access this value

the same way for both objects, much like how submitter is set up in

ReviewRequestDraft.

All unit tests pass.