Migrate CEC enabled value to CEC configuration

Read value whether HDMI CEC is enabled from HdmiCecConfig and cache it
in HdmiControlService. This changes the type from boolean to int.

Adapt the @hide listener for a change of this value to return integers
instead of booleans as well.

Bug: 171870477
Test: atest com.android.server.hdmi

Change-Id: I6275fe1b3e1ca62c210019e1df216f8731a0b5ab