Trusted Hotword: Allow disabling periodic restarts.

Mitigates quality risk that may arise due to mismanaged state around the
restarts (either on the platform or application side).

The duration will be flag-controlled in a follow-up cl so it can
actually be disabled by flag.

Bug: 224618257
Test: manual
Change-Id: I3b17b47fab4120b42d75443b213be3c1ef5491aa
(cherry picked from commit b8cd0a42)
Merged-in: I3b17b47fab4120b42d75443b213be3c1ef5491aa