Find elements that ignore timestamps while they shouldn't

[mat-hek]

Kuba:

• [x] membrane_sdl_plugin - sink relies on framerate instead of timestamps https://github.com/membraneframework/membrane_sdl_plugin/pull/34
• [x] membrane_portaudio_plugin - source doesn't generate timestamps https://github.com/membraneframework/membrane_portaudio_plugin/pull/53
• [x] membrane_mp3_mad_plugin - decoder doesn't forward timestamps https://github.com/membraneframework/membrane_mp3_mad_plugin/pull/50
• [x] membrane_mp3_lame_plugin - encoder doesn't forward timestamps https://github.com/membraneframework/membrane_mp3_lame_plugin/pull/49
• [x] membrane_ogg_plugin - demuxer doesn't extract timestamps from the OGG container https://github.com/membraneframework/membrane_ogg_plugin/pull/10

Bartek:

• [x] membrane_ffmpeg_swresample_plugin - resampler doesn't forward timestamps https://github.com/membraneframework/membrane_ffmpeg_swresample_plugin/pull/57
• [x] membrane_flac_plugin - parser doesn't forward timestamps https://github.com/membraneframework/membrane_flac_plugin/pull/24
• [x] membrane_opus_plugin - we don't set the timestamp here https://github.com/membraneframework/membrane_opus_plugin/pull/60
• [x] membrane_aac_fdk_plugin - we don't set the timestamp here https://github.com/membraneframework/membrane_aac_fdk_plugin/pull/54