[BETA] Add OpenAI /images/variations + Topaz API support (#7700)

* feat(main.py): initial commit for `/image/variations` endpoint support

* refactor(base_llm/): introduce new base llm base config for image variation endpoints

* refactor(openai/image_variations/transformation.py): implement openai image variation transformation handler

* fix: test

* feat(openai/): working openai `/image/variation` endpoint calls via sdk

* feat(topaz/): topaz sync image variation call support

Addresses https://github.com/BerriAI/litellm/issues/7593

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* fix(topaz/transformation.py): fix linting errors

* fix(openai/image_variations/handler.py): fix passing json data

* fix(main.py): image_variation/

support async image variation route - `aimage_variation`

* fix(test_get_model_info.py): fix test

* fix: cleanup unused imports

* feat(openai/): add async `/image/variations` endpoint support

* feat(topaz/): support async `/image/variations` calls

* fix: test

* fix(utils.py): fix get_model_info_helper for no model info w/ provider config

handles situation where model info is not known but provider config exists

* test(test_router_fallbacks.py): mark flaky test

* fix: fix unused imports

* test: bump otel load test perf threshold - accounts for current load tests hitting same server

tests/local_testing/test_router_fallbacks.py

@@ -757,6 +757,7 @@ async def test_async_fallbacks_max_retries_per_request():
         router.reset()
 
 
+@pytest.mark.flaky(retries=6, delay=2)
 def test_ausage_based_routing_fallbacks():
     try:
         import litellm
@@ -1357,6 +1358,7 @@ def test_router_fallbacks_with_custom_model_costs():
 
     Goal: make sure custom model doesn't override default model costs.
     """
+
     model_list = [
         {
             "model_name": "claude-3-5-sonnet-20240620",