[MLIR] Fix FileCheck annotations and add 32-bit coverage (#167149)
Addresses #93154 by ensuring the test RUN/FILECHECK prefixes across
`mlir/test/Conversion/FuncToLLVM/` and related files match their
expected outputs, and adds an `index-bitwidth=32` variant of
`expand-then-convert-to-llvm.mlir` that exercises
`@collapse_shape_dynamic_with_non_identity_layout` through the same
MemRef-to-LLVM pipeline so the 32-bit layout descriptors are verified.