[red-knot] PEP 561 compliant module resolver

[carljm]

(Or intentional choices to diverge from PEP 561 compliance.)

Subtasks:

• [x] Vendor typeshed's stubs: https://github.com/astral-sh/ruff/pull/11340
• [x] Add automation for keeping typeshed's stubs up to date: https://github.com/astral-sh/ruff/pull/11427
• [x] Implement --custom-typeshed-dir internally: https://github.com/astral-sh/ruff/pull/11767
• [x] Implement the typing spec's module resolution order:
  • https://github.com/astral-sh/ruff/pull/11767
  • Proposal for tweaking the spec posted at https://discuss.python.org/t/pep-561-s-module-resolution-order-seems-incorrect/55048/1
• [x] Make vendored typeshed stubs available from the built Ruff binary: https://github.com/astral-sh/ruff/pull/11779
• [x] Use vendored typeshed stubs at runtime to resolve symbols to stdlib definitions if --custom-typeshed-dir is not passed
  • [x] Add a VendoredFileSystem implementation: https://github.com/astral-sh/ruff/pull/11863
  • [x] Use the VendoredFileSystem implementation to resolve stdlib stubs: #12224
• [ ] Add support for stubs packages suffixed with -stubs installed into site-packages (must take priority over other packages installed into site-packages)
• [x] Add support for typeshed's VERSIONS file: we shouldn't fallback to a typeshed module if the VERSIONS file specifies it does not exist with the --target-version the user passes.
  • [x] Add a parser for VERSIONS: https://github.com/astral-sh/ruff/pull/11836
  • [x] Use the VERSIONS file when resolving stdlib modules: https://github.com/astral-sh/ruff/pull/12141
• [x] Add support for editable installs that use static ._pth files:
  • [x] https://github.com/astral-sh/ruff/pull/12289
  • [x] https://github.com/astral-sh/ruff/pull/12307
• [ ] Fix #12278
• [ ] Audit mypy's and pyright's module resolvers to see if there's anything that's not in the spec that still needs to be implemented

[MichaReiser]

One thing that we need to implement as part of this is a vendored filesystem. It's not a functionality but a task to complete on our way to get there.

[AlexWaygood]

One thing that we need to implement as part of this is a vendored filesystem. It's not a functionality but a task to complete on our way to get there.

Right. I was considering that part of

Use vendored typeshed stubs at runtime to resolve symbols to stdlib definitions if --custom-typeshed-dir is not passed

since, as you say, it's necessary to implement a vendored filesystem in order to be able to do that