Following on the plan of isolating the compiler/mlir/hlo directory.
Another xla_lhlo dialect will be created under compiler/mlir/xla/ later.
PiperOrigin-RevId: 320210326
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