[Task]: Move beam-sdks-java-io-google-cloud-platform test implementations to test scope

### What needs to happen?

This eliminates unwanted junit and hamcrest dependencies in main artifact. Also need to move `@Internal` TestBigQuery and TestPubsub classes which depend on these test libraries to the test artifact. In the long term, use textFixture (#18593)

### Issue Priority

Priority: 2 (default / most normal work should be filed as P2)

### Issue Components

- [ ] Component: Python SDK
- [X] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [X] Component: IO connector
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
- [ ] Component: Samza Runner
- [ ] Component: Twister2 Runner
- [ ] Component: Hazelcast Jet Runner
- [ ] Component: Google Cloud Dataflow Runner