Rename use-hermes-nightly.js to use-hermes-prebuilt.js (#56750)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/56750

Rename scripts/releases/use-hermes-nightly.js to scripts/releases/use-hermes-prebuilt.js.
The script fetches the latest prebuilt Hermes from the 'latest-v1' npm dist-tag, not a
true 'nightly' build. Update:
- Script name: use-hermes-nightly.js -> use-hermes-prebuilt.js
- Internal log message: 'nightly update' -> 'prebuilt update'
- Import: updateHermesVersionsToNightly -> updateHermesVersionsToPrebuilt
- CI step names: 'Set nightly Hermes versions' -> 'Set Hermes prebuilt version'
- Script path references in test-all.yml, test-ios-helloworld/action.yml,
  test-ios-rntester/action.yml

## Changelog:
[Internal] -

Reviewed By: cortinico

Differential Revision: D104649633

fbshipit-source-id: ea74dbdba5a7f31aa58e5f581249e384581e6620