Rename resharding CoordinatorStateEnum kCommitted to kDecisionPersisted and remove kRenaming

CoordinatorStateEnum::kRenaming and the current CoordinatorStateEnum::kCommit can be merged into one state.

Additionally, as foundation for error handling in resharding, CoordinatorStateEnum::kCommit should be renamed to CoordinatorStateEnum::kDecisionPersisted. Once the coordinator is in the new state, the resharding operation finalizes whether it will commit or abort - the decision may not be changed while the rest of the operation completes.