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

[Abacn]

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
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• 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