Android longPress to initiate PointAnnotation draggable

[lochstar]

Description

This change is based on an old discussion at #3425.

When multiple draggable PointAnnotation are visible on a pan-able map, it is very easy to accidentally trigger the drag event of the PointAnnotation whilst moving around the map.

This issue only exists on Android, iOS already implements a long-press to start the drag. This PR aligns the behaviour.

How to verify

Example App > Show Point Annotation: tap selects, longPress then drag fires onDrag.

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Whilst testing in the example app, I noticed there is a crash when pressing "Render Polygon above", I've added asStringOrNull check to both setAboveLayerID and setBelow. Let me know if you want me to add the same to any of the other functions, e.g. setSourceLayerID.

Checklist

• I've read CONTRIBUTING.md
• I updated the doc/other generated code with running yarn generate in the root folder
• I have tested the new feature on /example app.
  • In V11 mode/ios
  • In New Architecture mode/ios
  • In V11 mode/android
  • In New Architecture mode/android
• I added/updated a sample - if a new feature was implemented (/example)