AxisInfo analysis currently retrieves the rank from any `ShapedType`
producing `PoisonOp`. This is a problem if the `PoisonOp` actually
produces a `MemDesc`, since the value produced by the `PoisonOp` may
flow into the same value as some other `MemDesc` producing operation,
which will have been assigned the "pessimistic state" and have rank 1.

When we attempt to join the two, the ranks will not match, potentially
resulting in a crash.

- [x] I am not making a trivial change, such as fixing a typo in a
comment.

- [x] I have written a PR description following these
  [rules](https://cbea.ms/git-commit/#why-not-how).

- [x] I have run `pre-commit run --from-ref origin/main --to-ref HEAD`.

- Select one of the following.
  - [x] I have added tests.
    - `/test` for `lit` tests
    - `/unittest` for C++ tests
    - `/python/test` for end-to-end tests
  - [ ] This PR does not need a test because `FILL THIS IN`.

- Select one of the following.
  - [ ] I have not added any `lit` tests.
- [x] The `lit` tests I have added follow these [best
practices](https://mlir.llvm.org/getting_started/TestingGuide/#filecheck-best-practices),
including the "tests should be minimal" section. (Usually running Python
code
    and using the instructions it generates is not minimal.)

Signed-off-by: Witold Dziurdz <[email protected]>