Implement mode for CEC power control of connected TV and Audio System

Added 'TV + Audio System' to the possible values and implemented the functionality.

Updated naming of some local variables that were still using the old
name 'send_standby_on_sleep'.

Test: atest com.android.server.hdmi
Bug: 174821495
Change-Id: I87e9ea4029b0a61acbf85308a59470322fda53ae