Equalizer: Improvements & layout fixes

This merge request brings several improvements to the equalizer with:

• The default pre-amp value that is now only set when the equalizer is disabled as the other profiles already set a value of their own for the pre- amplification.
• The EqualizerView that is now aligned to the AudioPlayerView's safe area in order to avoid any visual glitch.
• The constraints updates of the toggle view that are now performed along with the animation and the completion is updated to avoid any unexpected behaviours.

This merge request also brings a small refactor to the Reset feature:

• Pressing the reset button of the equalizer now resets the equalizer according to the current profile's values instead of applying a value of 0 for all the bands without disabling the equalizer.

Closes #1829 (closed)

EqualizerView's layout improvements

changed milestone to %3.5.9

added Bug Interface Player labels

approved this merge request

added 5 commits

• 6652f086 - 1 commit from branch videolan:master
• 4cc32999 - AudioPlayerViewController: Align the Equalizer view to the SafeArea
• 32e0deaa - VLCPlaybackService: Fix the pre-amp value attribution
• f4eb7eb3 - EqualizerView: Refactor the reset feature
• 69ec6c20 - SpoilerButton: Fix the hiding of the toggle view

Compare with previous version

enabled an automatic merge when the pipeline for 69ec6c20 succeeds

merged