Check hidden API exemptions

Refuse to deal with newlines and null characters in
HiddenApiSettings.update(). Also disallow nulls in process start
arguments.

Bug: 316153291
Test: Treehugger for now
(cherry picked from commit 7ba059e2)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:60669aa49aba34c0950d6246bd95b54f91a3c8e8)
Merged-In: I83cd60e46407a4a082f9f3c80e937dbd522dbac4
Change-Id: I83cd60e46407a4a082f9f3c80e937dbd522dbac4