Some fixes to MCP tests. And a bunch of fixes for Vector providers.
I also enabled a bunch of Vector IO tests to be used with
`LlamaStackLibraryClient`
## Test Plan
Run Responses tests with llama stack library client:
```
pytest -s -v tests/integration/non_ci/responses/ --stack-config=server:starter \
--text-model openai/gpt-4o \
--embedding-model=sentence-transformers/all-MiniLM-L6-v2 \
-k "client_with_models"
```
Do the same with `-k openai_client`
The rest should be taken care of by CI.
This PR kills the verifications infrastructure which is no longer used.
It was relocated to the `llama-stack-evals`
(https://github.com/meta-llama/llama-stack-evals) repository previously.
Responses tests used this infrastructure but that wasn't quite
necessary, just a little useful back when @bbrownin introduced the
tests. On Discord, we agreed that tests can be moved to our regular
integrations test infra.
## Test Plan
Some tests currently do fail (although they run!) I will send a
follow-up PR which makes them all pass.
