Enable MLGO for register allocation

This enables Machine Learning Guided Optimizations (MLGO) for register
allocation. App launch performance on oriole-userdebug is improved by
0.53%, and binary size is very slightly reduced (e.g. 64 bytes for
libart.so).

https://dashboards.corp.google.com/_0e1b06dd_a79e_4433_b625_b62e5cac004b?p=BootImageProfileId:36265

Test: presubmit
Bug: 229056536
Change-Id: I0e5d40bb90a1555a1343f114ebffffca281f20b2