Fix HotwordDetectedResult phrase and extras.

Requiring hotword phrases to be listed in the manifest is punted to T.
A simple limited phrase ID is used for now.

Use PersistableBundle for the extras so that remotable objects cannot be
passed through it.

Bug: 182788844
Bug: 168305377
CTS-Coverage-Bug: 183425641
Test: builds
Change-Id: I9c1472b586f737788cc10d8dd7e023f348763392