Adds LPP sensitivity for Assistant invocation

Test: Cherrypick ag/15542611
Test: Ensure Assistant invocation is set as the LPP action
Test: Adjust LPP sensitivity
Test: Hold LPP for the set time
Test: Observe activation duration matches set time
BUG: 192995149
Change-Id: I820a9d83fd56bfa9ca978e82eb779cf3d519a5ab