Integrate LLVM at f4be6812e203690073280b9ac8d60092d75bbdce (iree-org#…

…18019)

Advance to llvm/llvm-project@f4be6812

New local patch:
* Reverting llvm/llvm-project@f6431f0c
(llvm/llvm-project#99890). Discussion:
https://discord.com/channels/689900678990135345/1266421307285966859
* This caused new compile failures in our CUDA flow. We suspect our
usage of upstream passes/patterns need some updates in this repo.
Reverting for now to give ourselves some time to investigate.

Existing local patches carried over:
* Still carrying a revert of
llvm/llvm-project@fa06668
* Still carrying a revert of
llvm/llvm-project@bbd4af5

Dropped local patches:
* No longer carrying a local patch of
llvm/llvm-project@4f80508

Signed-off-by: Benoit Jacob <[email protected]>