Synchronize submodules with LLVM at llvm/llvm-project@18ec93d9e60c

Updates LLVM dependencies to match
[18ec93d9e60c](https://github.com/llvm/llvm-project/commit/18ec93d9e60c).
- TensorFlow to
[0c225ef7450a](https://github.com/tensorflow/tensorflow/commit/0c225ef7450a)
- MLIR-HLO to
[7e00576f3f1e](https://github.com/tensorflow/mlir-hlo/commit/${MLIR_HLO_SHA?})

`./scripts/git/update_to_llvm_syncpoint.py`

Automated submodule bump from .github/workflows/update_llvm_dependent_submodules.yml

PiperOrigin-RevId: 388271373