[Feature Request] View masking previews

### Problem Statement

I am integrating Session Replay in a React native based app with some custom masking rules. Each time I need to check how the view is masked, I have to run the app, wait for the session to appear on sentry, scroll the video to find my target screen and finally check the masking. Repeat until I've got it right.

This is very tedious to do and is error-prone.

### Solution Brainstorm

Add a `SentryMaskPreview` component that can be used to render a masked child component. We can then rely on hot-reload to get a quick feedback loop when implementing custom masking logic.

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The iOS native feature request:
[https://github.com/getsentry/sentry-cocoa/issues/4633]()

The issue names no files, tests, or entry points. Start by reviewing the linked sentry-cocoa request and the existing React Native masking and Session Replay implementation; done means providing a SentryMaskPreview component that renders a masked child and supports a quick hot-reload feedback loop.

索引モデルが issue の本文から書いたものです。