frontend: Add ability to collapse volume controls

[cg2121]

Description

This is an alternative to hiding the volume controls completely when they are hidden.

Horizontal volume controls:

Vertical volume controls:

Motivation and Context

Idea from @Warchamp7 in #7819

How Has This Been Tested?

Hid/unhid volume controls and made sure the UI looked correct.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[WizardCM]

I like the idea personally, but wonder if they should have some indicator when collapsed that they're muted - either via an icon or by greying out the text.

[cg2121]

Updated to include @WizardCM's idea of graying out the name label when muted.

[cg2121]

#12735 replaces this.