A way to get the firebase-tools version from package.json instead of firebaseToolsVersion

### The use case you're trying to solve

I'm trying to make sure that the version of firebase-tools used is the same as what is in my package.json. `latest` will *probably* be fine most of the time but there might be issues later.

### Change to the action that would solve that use case

Add an option to read the version of firebase-tools version from package.json instead of requiring `firebaseToolsVersion` be set separately.

### Other considerations

Maybe I could use some other tooling to sync up my package.json with `firebaseToolsVersion` but it would be nicer if action-hosting-deploy could do it on its own.

Start by locating the action entry point that handles firebaseToolsVersion and the repository's package.json. Trace how the Firebase CLI version is selected, then check any existing tests for action inputs and version handling. Done means the action can use the firebase-tools version declared in package.json without requiring a separate firebaseToolsVersion value.

Written by the indexing model from the issue text.