Limit access to suspected false positives.

Members modified herein are suspected to be false positives: i.e. things
that were added to the greylist in P, but subsequent data analysis
suggests that they are not, in fact, used after all.

Add a maxTargetSdk=P to these APIs. This is lower-risk that simply
removing these things from the greylist, as none of out data sources are
perfect nor complete.

For APIs that are not supported yet by annotations, move them to
hiddenapi-greylist-max-p.txt instead which has the same effect.

Exempted-From-Owner-Approval: Automatic changes to the codebase
affecting only @UnsupportedAppUsage annotations, themselves added
without requiring owners approval earlier.

Bug: 115609023
Test: m
Change-Id: Ia937d8c41512e7f1b6e7f67b9104c1878b5cc3a0
Merged-In: I020a9c09672ebcae64c5357abc4993e07e744687