Add Fake TPU e2e Autoscaling Test Cases

[ryanaoleary]

Why are these changes needed?

This PR adds a fake TPU test case, similar to the existing fake GPU test case for autoscaling, that uses detached actors to verify that single-host and multi-host TPU autoscaling behave as expected. The behaviors tested included:

• (1) Creating a detached actor that requests resources: {"TPU": 4} will scale up a Ray TPU worker
• (2) For a multi-host worker group, the number of workers created should equal replicas * numOfHosts
• (3) Terminating detached actors scheduled on a multi-host worker group replica will cause the entire replica to be scaled down

Edit: Removed test behavior for idle nodes being scaled down, since this requires setting the timeout value to a much higher value and scaling down of multi-host replicas is still tested.

Related issue number

Checks

• [x] I've made sure the tests are passing.
• Testing Strategy
  • [x] Unit tests
  • [x] Manual tests
  • [ ] This PR is not tested :(