Bazel support for firebase emulator

**Is your feature request related to a problem? Please describe.**
There is no good way to execute tests via bazel via normal bazel commands if the emulator is required
**Describe the solution you'd like**
A bazel import from firestore that has a dependency on the emulator running and is able to determine if it needs to be spun up or not based on test targets being cached or not.
**Describe alternatives you've considered**
1. Creating custom bazel targets that are not cached that run with concurrently to run alongside the emulator.
2. Running the emulator outside of bazel, then running the bazel command. This will get caching, but I can't use bazel without the emulator then.

I was told to recreate this issue here per this https://github.com/googleapis/nodejs-firestore/issues/1469