redis otel tracing + async support for latency routing (#6452)

* docs(exception_mapping.md): add missing exception types

Fixes https://github.com/Aider-AI/aider/issues/2120#issuecomment-2438971183

* fix(main.py): register custom model pricing with specific key

Ensure custom model pricing is registered to the specific model+provider key combination

* test: make testing more robust for custom pricing

* fix(redis_cache.py): instrument otel logging for sync redis calls

ensures complete coverage for all redis cache calls

* refactor: pass parent_otel_span for redis caching calls in router

allows for more observability into what calls are causing latency issues

* test: update tests with new params

* refactor: ensure e2e otel tracing for router

* refactor(router.py): add more otel tracing acrosss router

catch all latency issues for router requests

* fix: fix linting error

* fix(router.py): fix linting error

* fix: fix test

* test: fix tests

* fix(dual_cache.py): pass ttl to redis cache

* fix: fix param

litellm/proxy/auth/user_api_key_auth.py

@@ -260,6 +260,7 @@ async def user_api_key_auth(  # noqa: PLR0915
                     headers=request.headers
                 ),
             )
+
         ### USER-DEFINED AUTH FUNCTION ###
         if user_custom_auth is not None:
             response = await user_custom_auth(request=request, api_key=api_key)  # type: ignore