Fix OTT devices not reacting to messages in Standby

Reverts most changes to Playback device message handling in Standby from
aosp/1970899, to fix CTS tests and avoid unexpected behavior changes.

aosp/1970899 has all devices use HdmiCecStandbyModeHandler, which causes
Playback devices to ignore or <Feature Abort> certain messages in
standby. This caused CTS failures for cect_hf_4_6_7 and
cect_11_2_2_1 (b/226366076).

This CL moves all behavior-affecting handlers except for <User Control
Pressed> (required for the fix in aosp/1970899) back to TVs only: it is
safer to preserve the original behavior until there is a reason to change it.

Test: atest CtsHdmiCecHostTestCases
Bug: 226366076
Change-Id: I888da78e27503ca0dada29e8a8b1f3d3fe03a608