Add ChannelsCount filtering when Selecting Audio Tracks

[jlnabais]

Have you read the FAQ and checked for duplicate open issues?
Yes I've checked the FAQ for anything related with this change and I've checked open issues for duplicates.

Is your feature request related to a problem? Please describe.

Currently if we have a DASH Manifest with 2 Languages and one of the languages has EAC-3 audio tracks both stereo and surround and another only with stereo we want to specify the channel count when swapping so we can select 6 channels (surround).

Partial example of Audio AdaptaionSets of a DASH Manifest:

<AdaptationSet Label="English" contentType="audio" group="2" lang="en-US" mimeType="audio/mp4" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
  (...)
  <Role schemeIdUri="urn:mpeg:dash:role:2011" value="main"/>
  <Representation audioSamplingRate="48000" bandwidth="102626" codecs="mp4a.40.2" id="audio_0_en-US_102626">
    <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"/>
    <SegmentTemplate timescale="48000" (...) startNumber="0">
      <SegmentTimeline>
        (...)
      </SegmentTimeline>
    </SegmentTemplate>
  </Representation>
</AdaptationSet>
(...)
<AdaptationSet Label="English" contentType="audio" group="2" lang="en-US" mimeType="audio/mp4" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
  (...)
  <Role schemeIdUri="urn:mpeg:dash:role:2011" value="main"/>
  <Representation audioSamplingRate="48000" bandwidth="100268" codecs="ec-3" id="audio_0_en-US_100268">
    <AudioChannelConfiguration schemeIdUri="tag:dolby.com,2014:dash:audio_channel_configuration:2011" value="A000"/>
    <SegmentTemplate timescale="48000" (...) startNumber="0">
      <SegmentTimeline>
        (...)
      </SegmentTimeline>
    </SegmentTemplate>
  </Representation>
</AdaptationSet>
(...)
<AdaptationSet Label="Spanish" contentType="audio" group="2" lang="es-ES" mimeType="audio/mp4" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
  (...)
  <Role schemeIdUri="urn:mpeg:dash:role:2011" value="main"/>
  <Representation audioSamplingRate="48000" bandwidth="100268" codecs="ec-3" id="audio_0_es-ES_100268">
    <AudioChannelConfiguration schemeIdUri="tag:dolby.com,2014:dash:audio_channel_configuration:2011" value="A000"/>
    <SegmentTemplate timescale="48000" (...) startNumber="0">
      (...)
    </SegmentTemplate>
  </Representation>
</AdaptationSet>
(...)
<AdaptationSet Label="English" contentType="audio" group="2" lang="en-US" mimeType="audio/mp4" segmentAlignment="true" startWithSAP="1" subsegmentAlignment="true" subsegmentStartsWithSAP="1">
  (...)
  <Role schemeIdUri="urn:mpeg:dash:role:2011" value="main"/>
  <Representation audioSamplingRate="48000" bandwidth="196268" codecs="ec-3" id="audio_0_en-US_196268">
    <AudioChannelConfiguration schemeIdUri="tag:dolby.com,2014:dash:audio_channel_configuration:2011" value="F801"/>
    <SegmentTemplate timescale="48000" (...) startNumber="0">
      <SegmentTimeline>
        (...)
      </SegmentTimeline>
    </SegmentTemplate>
  </Representation>
</AdaptationSet>

Describe the solution you'd like

We need to activate the support for channelCount on the lib/player.js selectAudioLanguage so we can select a given audio track with the same language/codec/role but different channelCount.

Describe alternatives you've considered

None, this was pretty straightforward, we already have a method to select the audio track so it felt like the right place to do so.

Additional context

PR raised: #4552

Regarding unit tests: It seems that the test/media/adaptation_set_criteria_unit.js file already has the relevant use cases to filter out the proper variant based on channelsCount.