Provide the way to enable/disable debug mode for logging egressed data

Currently we provide the Shell command to enable/disable one debug mode
that we will log the HotwordDetectedResult and HotwordRejectedResult if
the debug mode is wnable. But we will reset the debug mode after one
hour from last enable.

Bug: 194339253
Test: Use the Shell command and check the log
Change-Id: I212ad58c7550b297babed50249a08db6f0e24b3a