Detect nested workspace inside the current workspace and members with identical names (#9094)
## Summary
Align uv's workspace discovery with red knots (see
https://github.com/astral-sh/ruff/pull/14308#issuecomment-2474296308)
* Detect nested workspace inside the current workspace rather than
testing if the current workspace is a member of any outer workspace.
* Detect packages with identical names.
## Test Plan
I added two integration tests. I also back ported the tests to main to
verify that both these invalid workspaces aren't catched by uv today.
That makes this, technically, a breaking change but I would consider the
change a bug fix.
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Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>