Keep FileReader in DONE state after abort

[fallintoplace]

Summary:

Before #57375, reads never entered LOADING, so the active abort path was effectively unreachable. Now that reads use LOADING, that path calls _reset() before and after transitioning to DONE, leaving the reader in EMPTY after abort() returns.

This differs from the File API abort algorithm, which keeps an active reader in DONE. The final reset also overwrites a replacement read started by an abort handler, and that new read clears the shared _aborted flag before the canceled native promise settles.

This change:

• keeps an aborted active reader in DONE with a null result
• skips the old loadend if the abort handler starts another read
• gives each read an ID so a canceled native promise cannot complete over a newer read

Changelog:

[GENERAL] [FIXED] - Keep FileReader in the correct state after aborting a read.

Test Plan:

• yarn jest packages/react-native/Libraries/Blob/__tests__/FileReader-test.js --runInBand
• ./node_modules/.bin/prettier --check packages/react-native/Libraries/Blob/FileReader.js packages/react-native/Libraries/Blob/__tests__/FileReader-test.js
• ./node_modules/.bin/eslint --max-warnings 0 packages/react-native/Libraries/Blob/FileReader.js packages/react-native/Libraries/Blob/__tests__/FileReader-test.js
• yarn flow-check