XLA compilation options.

use_spmd_for_xla_partitioning Boolean. Whether to use XLA's SPMD partitioner instead of MPMD partitioner when compiler partitioning is requested.
enable_xla_dynamic_padder Boolean. Whether to enable XLA dynamic padder infrastructure to handle dynamic shapes inputs inside XLA. True by default. Disabling this may cause correctness issues with dynamic shapes inputs, as XLA will just assume the inputs are with padded shapes. However users can optionally set it to False to improve device time if masking is already handled in the user side.