feat: use uv for e2e-tests and add to devshell

[tgunnoe]

• replace requirements.txt with pyproject.toml. this brings the e2e-tests python environment in line with modern python projects. It also allows specifying others useful properties like linters and formatters

• add uv and uv.lock. uv is a modern python package manager that achieves both better speeds and reproducability through locking the exact dependencies required, much like Cargo.lock

• add these to the nix devshell

• bump omegaconf to the latest preview, because 2.3.0 included an older version of antlr4-python3-binary that used an older manifest version from the rest of the toolchain

Checklist

• Commit sequence broadly makes sense and commits have useful messages.
• The size limit of 400 LOC isn't needlessly exceeded
• The PR refers to a JIRA ticket (if one exists)
• New tests are added if needed and existing tests are updated.
• New code is documented and existing documentation is updated.
• Relevant logging and metrics added
• Any changes are noted in the changelog.md for affected crate
• Self-reviewed the diff

[ladamesny]

LGTM

[AmbientTea]

you mean to tell me there's a sane build tool for python? 🤨