[CI/CD] linting: share job steps up-to-and-including pip and lint dependency installation.

[jayaddison]

Feature or Bugfix

• Refactoring

Purpose

• By using identical job steps during the creation phases of linting-related jobs, it may be possible (I don't know whether it's implemented in practice) allow GitHub to re-use container images when running the relevant workflows. It's also a little more consistent.

Detail

• Installation of precise versions of ruff should occur as long as that is what is configured in pyproject.toml.
• For linting jobs, perform a pip upgrade install, followed by a .[lint] dependency set install.
• For mypy, where we also want to having typing information for some of the test dependencies, subsequently install those too (. should be detected as already-installed, I think?).

Relates

• bump ruff version #12065