* refactor(vertex_llm_base.py): Prevent credential misrouting for projects
Fixes https://github.com/BerriAI/litellm/issues/7904
* fix: passing unit tests
* fix(vertex_llm_base.py): common auth logic across sync + async vertex ai calls
prevents credential caching issue across both flows
* test: fix test
* fix(vertex_llm_base.py): handle project id in default cause
* fix(factory.py): don't pass cache control if not set
bedrock invoke does not support this
* test: fix test
* fix(vertex_llm_base.py): add .exception message in load_auth
* fix: fix ruff error