Use better formats for recording media

This issue should be tested in both iOS and Android, with different OS versions. In general, it should work the same everywhere except iOS with versions older than 14.3 where the native recorder will be used instead of the in-app recorder. This change affects recording audio files, for example when adding replies in forums or uploading private files. Instead of using an external app like previously, an in-app recorder will appear that should allow recording, pausing, and discarding audio without leaving the app. Here's some non-exhaustive instructions to test the basic use-cases: Open private files, and choose to upload an audio. Press the button to start recording, you should see time counting up and the recording ongoing. Press the pause button, the time should freeze and the recording stopped. Press the recording button to resume recording. Press the checkmark to stop the recording and see a preview of the audio. Listen to the audio preview, it should be what you recorded (make sure nothing was recording whilst the recording was paused). Press the button to delete the audio, and start the process again. This time, submit the audio from the paused state. After checking the final preview, submit the recording. Make sure that it's been properly uploaded as an mp3 file, and open it from the LMS to double-check that it's been recorded properly.