## Type of change
- [x] Feature
- [ ] Bugfix
- [ ] Technical
- [ ] Other :
## Content
This PR consists of several macro-blocks separated by path/package:
- `messages.impl.mediaplayer` : Global (room-wide) media player, now used only for voice messages but could be used for all media within EX in the future. It is backed by media3's exoplayer. Currently not unit-tested because mocking exoplayer is not trivial.
- `messages.impl.voicemessages.play` : Business logic of a timeline voice message. This is all the logic that manages the voice message bubble.
- `messages.impl.timeline.model` & `messages.impl.timeline.factories`: Timeline code that takes care of creating the `content` object for voice messages.
- `messages.impl.timeline.components` : The actual View composable that shows the UI inside a voice message bubble.
All the rest is just small related changes that must be done here and there in existing code.
From a high level perspective this is how it works:
- Voice messages are unlike other message bubbles because they carry state (i.e. playing, downloading...) so they have a Presenter managing this state.
- Media content (i.e. the ogg file) of a voice message is downloaded from the rust SDK on first play then stored in a voice messages cache (see the `VoiceMessageCache` class, it is just a subdirectory in the app's cacheDir which is indexed by the matrix content uri). All further play attempts are done from the cache without hitting the rust SDK anymore.
- Playback of the ogg file is handled with the `VoiceMessagePlayer` class which is basically a "view" of the global `MediaPlayer` that allow the voice message to only see the media player state belonging to its media content.
- Drawing of the waveform is done with an OSS library wrapped in the `WaveformProgressIndicator` composable.
Known issues:
- The waveform has no position slider.
- The waveform (and together with it the whole message bubble) is taller than the actual Figma design.
- Swipe to reply for voice messages is disabled to avoid conflict with the audio scrubbing gesture (to reply to a voice message you have to use the long press menu).
- The loading indicator is always shown (there is no delay).
- Voice messages don't stop playing when redacted.
## Motivation and context
https://github.com/vector-im/element-meta/issues/2083
## Screenshots / GIFs
Provided by Screenshot tests in the PR itself.
- Add additional states to preview.
- Add TODO description for commented code
- Move showUserDefinedSettingStyle from the node to the view for testability.
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