Expose experiment from ExperimentUnit.
Expose experiment from ExperimentUnit.

PiperOrigin-RevId: 432167146
Change-Id: I22b7f416de7b3c53855c255029883c00e47a5b1b
GitOrigin-RevId: 81ff2e98570eaf0b3e964ca760dafbb80d425874

deepmind/xmanager,deepmind/xmanager