Summary:
This PR renames ` hermes-inspector-msggen` to `react-native/hermes-inspector-msggen`, moves it to `packages/hermes-inspector-msggen` and makes the package private as part of RFC480.
Related to https://github.com/facebook/react-native/issues/34692
## Changelog
[General] [Changed] - Move and rename `hermes-inspector-msggen` to `react-native/hermes-inspector-msggen`
Pull Request resolved: https://github.com/facebook/react-native/pull/34850
Test Plan: run `sh ReactCommon/hermes/inspector/tools/run_msggen`
Reviewed By: mattbfb
Differential Revision: D40060406
Pulled By: cortinico
fbshipit-source-id: e018fd88e8374a69fbd8737fbb9abe7565d4a003
Gabriel Donadel Dall'Agnol