Updates LLVM usage to match [7e78d89052b1](https://github.com/llvm/llvm-project/commit/7e78d89052b1) PiperOrigin-RevId: 333090785
Also add a localized `mlir-hlo-opt` binary for the testing of tensorflow/compiler/mlir/hlo/... ; this directory is intended to be self-contained and depend only on MLIR. PiperOrigin-RevId: 319878984