Add button property mouse events

[HariniMalothu17]

Description

Adds support for detecting which mouse button triggered pointer events (left, right, middle, etc.)
and registers missing W3C pointer event handlers in the native event system.

Type of Change

Erase all that don't apply.

• Bug fix (non-breaking change which fixes an issue)

Why

PointerEvent.button and PointerEvent.buttons were always 0 in JS pointer events (onPointerDown, onPointerUp), making it impossible to distinguish right-clicks from left-clicks. Additionally, several W3C pointer event handlers (onPointerDown, onPointerUp, onClick, etc.) were never registered in the native event bitset because BaseViewProps::setProp() was missing their VIEW_EVENT_CASE entries.

Resolves #15827 #6410

Screenshots

Testing

Tested in playground

Optional: Describe the tests that you ran locally to verify your changes.

Changelog

Should this change be included in the release notes: yes

Add a brief summary of the change to use in the release notes for the next release.

Microsoft Reviewers: Open in CodeFlow

[HariniMalothu17]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[acoates-ms]

Rather than just adding a playground sample, can you add an actual test page to RNTester, and a E2E test that verifies the behavior so we can verify it doesn't break in the future.

[acoates-ms]

Are you sure you need the BaseViewProps.cpp fork? It doesn't look like you are using those new properties?

[HariniMalothu17]

Are you sure you need the BaseViewProps.cpp fork? It doesn't look like you are using those new properties?

Yes, the BaseViewProps.cpp fork is needed. The upstream BaseViewProps.cpp was missing VIEW_EVENT_CASE entries for several W3C pointer event handlers (onPointerDown, onPointerUp, onClick, etc.) in setProp(). Without these entries, the native event bitset never registers these handlers, so pointer events don't fire. I've also contributed this fix upstream to React Native so the fork can be removed once the upstream update is pulled in.
facebook/react-native#56188