Fix test flake and add uv dev dependency

[cicdw]

Closes #15077

Additionally:

• adds uv as a dev dependency
• enforces pydantic>=2.9.0 in generating openAPI schema to avoid noisy commits

[cicdw]

@desertaxle let me know if this isn't maintaining the spirit of this test and i can revisit

[desertaxle]

I'd say it's mostly in the spirit. One of the things this test was checking was that reads will block until the lock is released. I think it's still worth it to have a test for that, but removing the flake is more important.

[codspeed-hq]

CodSpeed Performance Report

Merging #15251 will not alter performance

_{Comparing fix-test-flake (fb3d1c4) with main (8ecdce4)}

Summary

✅ 3 untouched benchmarks

[zzstoatzz]

defer to alex on the spirit on the test but uv change looks 👌