Fix wrong behaviour when move multiple files out of watched folder on mac (dotnet...

Fix wrong behaviour when move multiple files out of watched folder on mac (dotnet/corefx#41963)

* FS

watcher

* Multiple rename macOS fix

* Multiple rename macOS fix

* Format code

* Clean proj file

* Apply PR comments

* Apply suggestions from code review

Co-Authored-By: Cory Nelson <phrosty@gmail.com>
* Update src/System.IO.FileSystem.Watcher/src/System/IO/FileSystemWatcher.OSX.cs

Co-Authored-By: Stephen Toub <stoub@microsoft.com>
* Apply PR comments

* Apply PR comments

* Apply PR comments

* Document rename event id behaviour

Commit migrated from https://github.com/dotnet/corefx/commit/a1f8c919ac1280bb235264d5cc81f23b0d117710