MacOS mouse events show up at wrong locations

[HeyImChris]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native 👍
• [X ] I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

There's a bug where mac os events are received with locations relative to either the screen or the window. Different click styles (light trackpad tap vs. harder trackpad click) appear to dictate which event type we have and thus, which coordinate system we're receiving events in. Right now we were treating every click as if the event location is relative to the window, but we receive some click events relative to the screen. We need to handle those and convert them properly to the right coordinate system.

There's an unknown of why these aren't just MouseDown/MouseUp events. It's possible React Native is gobbling up the OS events somewhere and giving these back, but a search of the repo found no obvious NSEventType manipulation. This did reveal a tangential bug in RNTester where every other mouse down event is throwing an RCTAssert on MacOS which eats up that event. I'm looking into that bug next.

Focus areas to test

• Soft tap the CommandButton in a downstream app (Polyester) to test dropping a menu at the correct location
• Click the CommandButton in a downstream app (Polyester) to test dropping a menu at the correct location
• Tweak the RNTester code so our ActionSheetExample on MacOS passes in an anchor ref we can trigger events off of. From there, soft tap and click a button and verify the menu drops in the correct location

Microsoft Reviewers: Open in CodeFlow