Fix renames of files that existed before we started watching on macOS

[devongovett]

T-371 T-609

This fixes renames on macOS so that the delete event for the old name is properly emitted along with the create event for the new name. There was a test for this, but it only covered the case where the original file was created after we started watching. If the file already existed, only the create event for the new name would be emitted.

This removes the checking of our map to see if the file was created previously (obviously wrong 🙈). This does mean, however, that more unnecessary delete events will be emitted in the case of quick events (e.g. create + delete) because macOS coalesces events, but we will just ignore them anyway if they aren't in the graph.

[height]

This pull request has been linked to 2 tasks:

• T-371 Watcher does not always emit delete event on renames (unlink task)
• T-609 Changing a File extension does not invalidate cache (unlink task)

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