Move Hermes setup in a dedicated ruby file

[cipolleschi]

Summary:
This Diff continue the effort of refactor and test the cocoapods script, moving hermes setup in a dedicated hermes.rb file and adding some tests on the logic of the hermes handling.

Changelog

[iOS][Changed] - move and test Hermes setup from react_native_pods script into a dedicated file

Differential Revision: D37522432

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D37522432

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	7,830,116	-232
android	hermes	armeabi-v7a	7,216,498	-208
android	hermes	x86	8,139,019	-258
android	hermes	x86_64	8,120,749	-269
android	jsc	arm64-v8a	9,695,700	-244
android	jsc	armeabi-v7a	8,451,163	-196
android	jsc	x86	9,646,317	-255
android	jsc	x86_64	10,244,130	-274

Base commit: d6c08bd
Branch: main

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: d6c08bd
Branch: main

[react-native-bot]

This pull request was successfully merged by @cipolleschi in 468b86b.

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