Revive MLIR interpreter.
Revive MLIR interpreter.

This is needed for debugging MLIR emitters. So far, the new GPU ops aren't
supported. This just reverts the deletion, with a few changes:

- removal of depreacted dialects (gml_st, thlo, lhlo, deallocation, xla CPU, xla rt)
- adjustments for upstream changes (expand_shape, vector combiners, scf.parallel)
- removal of mhlo ComputeReshapeShape
- replacement of tsl::Status with absl::Status
- move it out of mlir_hlo and adjust to TF style guide (...mostly)

The tooling still needs to be hooked up to the GPU compiler.

Reverts changelist 568496965
