Update Thift Pool metrics to use class qualname

[selfcommit]

💸 TL;DR

Copied and updated from @ckwang8128:
The __name__ directive will use Iface as the pool label for every single thrift pool defined for a service, since the Thrift compiler uses Client as the class.

We likely want __qualname__ instead to get a more identifiable label for these pool metrics.

📜 Details

Going forward the label will change from IFace to the full object reference.
Example:
Iface -> TestThriftContextFactory.context_factory.<locals>.Iface

🧪 Testing Steps / Validation

I've locally run docker-compose run baseplate make test and updated the thrift tests to reflect the change.

✅ Checks

• CI tests (if present) are passing
• Adheres to code style for repo
  - [ ] Contributor License Agreement (CLA) completed if not a Reddit employee

[ckw4ng]

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