Refactor of voice message playing code

[julioromano]

After PR review suggestions from @jonnyandrew
User facing functionality doesn't change, but overall architecture and testing is better.

[jonnyandrew]

Really nice, thank you!

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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0 Vulnerabilities
0 Security Hotspots
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[codecov]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (71ef76a) 63.21% compared to head (b96bb7e) 63.20%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1643      +/-   ##
===========================================
- Coverage    63.21%   63.20%   -0.01%     
===========================================
  Files         1201     1201              
  Lines        31199    31207       +8     
  Branches      6446     6447       +1     
===========================================
+ Hits         19721    19724       +3     
- Misses        8518     8523       +5     
  Partials      2960     2960              

Files	Coverage Δ
...pl/voicemessages/timeline/VoiceMessagePresenter.kt	91.89% <100.00%> (-2.34%)	⬇️
...oid/libraries/matrix/test/media/FakeMediaLoader.kt	46.66% <100.00%> (+3.80%)	⬆️
...pl/voicemessages/timeline/VoiceMessageMediaRepo.kt	89.28% <89.28%> (ø)
.../impl/voicemessages/timeline/VoiceMessagePlayer.kt	72.34% <65.38%> (-0.64%)	⬇️

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