Replace Fusebox setClientMetadata handshake with ReactNativeApplicationModel

[huntie]

Summary

Depends on facebook/react-native#47962.

In an aim to simplify the rn_fusebox.ts entry point, drops our use of FuseboxClient.setClientMetadata as a RNDT-client-identifying handshake, in favour ReactNativeApplication.enable.

• Replace FuseboxClientMetadataModel with existing ReactNativeApplicationModel
  • Now auto-inits, registration call is moved to rn_fusebox.ts (IMO, correctness fix that now includes this model only for this entrypoint).
  • Migrate rnPerfMetrics calls over (unchanged).
• Remove CDP definitions for FuseboxClient domain.

Test plan

[Incoming]

• This change maintains backwards compatibility with previous Local Storage data (if modifying settings, experiments, or other persisted client state).

Upstreaming plan

• This commit should be sent as a patch to the upstream devtools-frontend repo. I've reviewed the contribution guide.
• This commit is React Native-specific and cannot be upstreamed.