feat: add evaluations client passthrough and tests

[nborges-aws]

Description of changes:

• Add __getattr__ passthrough with accept_snake_case_kwargs to EvaluationClient
• Control plane allowlisted methods (10):
  • Evaluator CRUD: create_evaluator, get_evaluator, list_evaluators, update_evaluator, delete_evaluator
  • Online evaluation config CRUD: create_online_evaluation_config, get_online_evaluation_config, list_online_evaluation_configs, update_online_evaluation_config, delete_online_evaluation_config
• Data plane allowlisted methods (1):
  • evaluate
• Add *_and_wait polling methods using shared wait_until/wait_until_deleted utilities:
  • create_evaluator_and_wait, update_evaluator_and_wait, delete_evaluator_and_wait
  • create_online_evaluation_config_and_wait, update_online_evaluation_config_and_wait, delete_online_evaluation_config_and_wait
• All *_and_wait methods accept WaitConfig for configurable polling behavior and apply convert_kwargs for snake_case support
• Changes are additive — existing run() method and its helpers are untouched

Test plan:

• Unit tests (13 new):
  • Passthrough: CP forwarding, DP forwarding, snake_case conversion, AttributeError on unknown method, CP allowlist contents, DP allowlist contents
  • *_and_wait: create_evaluator_and_wait (success + failure), update_evaluator_and_wait, create_online_evaluation_config_and_wait, update_online_evaluation_config_and_wait, delete_evaluator_and_wait, delete_online_evaluation_config_and_wait
• Integration tests (13 total):
  • Passthrough (5): list_evaluators, list_evaluators with snake_case, get_evaluator on built-in, list_online_evaluation_configs, non-allowlisted method raises
  • Evaluator CRUD (4): create_evaluator_and_wait → get_evaluator → update_evaluator_and_wait → delete_evaluator_and_wait
  • Online evaluation config CRUD (4): create_online_evaluation_config_and_wait → get_online_evaluation_config → update_online_evaluation_config_and_wait → delete_online_evaluation_config_and_wait

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[github-actions]

✅ No Breaking Changes Detected

No public API breaking changes found in this PR.

[Hweinstock]

should we consolidate these two? Also, is there a DELETE_FAILED? I know there are for other primitives but not confident on evaluators.

[nborges-aws]

Yep will consolidate. I checked the service models, evaluators has DELETING, but no DELETE_FAILED

[Hweinstock]

should we verify the description actually updated?

[nborges-aws]

yep will add assertion