Allow StorageOptions to override storage host

[JaredEzz]

Is your feature request related to a problem? Please describe. To be able to use Firebase emulator and Firebase storage. I need to be able to override host.

Describe the solution you'd like Allow us to pass StorageOption to FirebaseOption, to allow manually setting project id and host

This is discussed in https://github.com/firebase/firebase-admin-java/issues/874 and would solve that issue by allowing us to set the host directly instead of trying to use a non-standard env variable that doesn't even work

@regine-chan submitted this commit in a PR https://github.com/firebase/firebase-admin-java/pull/826 but it was abandoned, so I'm reviving the fix since we have a need