Add support for building using Metro

[blakef]

Summary: Adds app to allow building and serving your React Native app in a similar structure to the boostrap and build tasks. This is the more comprehensive followup to D57067040.

Changelog: [Internal]

Differential Revision: D57067039

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D57067039

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	19,495,278	+22
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	22,867,559	-4
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: 9da65469671a9ec3c77bb891da04c62fb3f36de1 Branch: main

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D57067039

[facebook-github-bot]

This pull request has been merged in facebook/react-native@2fd7733137b7d7ae44ec42ef146d758ceeefc23e.