feat: add JS support for CSS mask properties

[paradowstack]

Rebase Note:

This branch is stacked on #54995 + #54996 + #54994 (Nishan's url() in background-image work). Once this work lands, this branch has to be rebased. Review only the last commit.

Summary:

This PR adds support for the mask-image, mask-size, mask-position and mask-repeat CSS properties. It follows the CSS spec described here. A mask clips a view and its whole subtree to the alpha channel of a gradient or an image. The remaining mask properties (mask-clip, mask-origin, mask-mode, mask-composite) and the mask shorthand are not covered here and can be added in a follow up PR if needed.

Every mask-* property accepts exactly the same values as its background-* counterpart, so the whole value pipeline is shared instead of duplicated - the same JS style processors and the same C++ prop conversions. url() masks are collected by the same shadow node code that requests background-image sources, so they go through the existing image loading path.

Work has been split into three stacked PRs for more convenient reviewing process:

1. this PR - style attributes, Flow types and the cross platform prop plumbing in C++
2. iOS - iOS rendering and the RNTester example page
3. Android - Android rendering

Changelog:

[GENERAL] [ADDED] - Add JS support for CSS mask properties

Test Plan:

• yarn fantom packages/react-native/Libraries/Components/View/__tests__/View-mask-itest.js
• yarn flow-check, yarn build-types (ReactNativeApi.d.ts regenerated)

Rendering is covered in the iOS and Android PRs on top of this one.

[github-actions]

Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

• Please include a clear changelog message.
• This change will be subject to additional review.

This change was flagged as: POTENTIALLY_BREAKING