Rework actions for detecting support for <Set Audio Volume Level>.

Removes GiveFeaturesAction, as it is unnecessary: HdmiCecNetwork already
handles <Report Feature>, so the action's job can accomplished by just
sending <Give Features> independently.

<Feature Aborts> for <Set Audio Volume Level> messages are now handled
in HdmiCecNetwork, because they indicate (lack of) support for the
message regardless of whether a SetAudioVolumeLevelDiscovery action is
active.

Bug: 205817429
Test: atest SetAudioVolumeLevelDiscoveryActionTest
Change-Id: I1383a980938ac181920f6d5d3f2ff9ad6c2e57ce