Expose process-state constant as a test api

This needs to be used in a cts test and so it is good to have it
annotated as such.

Test: Manually verify that its stubs are generated in the correct txt.

Bug: 304347838

Merged-In: I5a6f30cdb76a37f5ff412339a0d78e98991fe86e
Change-Id: I5a6f30cdb76a37f5ff412339a0d78e98991fe86e