Summary:
`_labelsForTags` is an array with string labels used only for local profiling, that we had to manually keep it in sync with `RCTPLTag`. Refactor so labels are assigned with switch instead.
Changelog: [iOS] Refactor: Assign string label to each case in RCTPLTag enum for startup performance logging
Reviewed By: fkgozali
Differential Revision: D32889043
fbshipit-source-id: 81da592a160a31b91e78289be0990cc2ff960f29
Paige Sun