feat(openai_movement): Change URL structures to kill /openai/v1 (part 1) (#3587)

The `/v1/openai/v1` prefix is annoying and now unnecessary given our
clearer focus on how to think about the API surface.

Let's kill it for the 0.3.0 update.

To make client-side changes feasible, we will do this in two parts. This
part adds a new route (sans `/openai/v1`) so the existing client
continues to work since the server supports both.

The next PR will be client-side (Stainless) changes which I will be
making shortly.

The final PR will remove the `/openai/v1` routes. 

Note that all these changes will happen rapidly within this release
cycle. The entire set _will be backwards incompatible_.

Author: ashwinb

.github/workflows/conformance.yml

@@ -66,6 +66,4 @@ jobs:
       # This step will fail if incompatible changes are detected, preventing breaking changes from being merged
       - name: Run OpenAPI Breaking Change Diff
         run: |
-          oasdiff breaking --fail-on ERR base/docs/static/llama-stack-spec.yaml docs/static/llama-stack-spec.yaml --match-path '^/v1/openai/v1' \
-          --match-path '^/v1/vector-io' \
-          --match-path '^/v1/vector-dbs'
+          oasdiff breaking --fail-on ERR base/docs/static/llama-stack-spec.yaml docs/static/llama-stack-spec.yaml --match-path '^/v1/'