Integrate LLVM at llvm/llvm-project@a28e7f1aad3e (iree-org#21520)

Revert commits:
-
llvm/llvm-project@b6a98b9:
It is not clear if we should only capture the conversion failure once or
not. Asking a question here:
llvm/llvm-project#150982 (comment)
-
llvm/llvm-project@330a7e1:
see iree-org#21522

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Signed-off-by: hanhanW <[email protected]>

Author: hanhanW