sound@cinnamon.org: add a key binding to switch active audio output device

[rostidev]

Demonstration of this new functionality is in the attached video below. Suggest to watch with sound turned on.

20260617_105708_compressed.mp4

Almost the same change is tested by me on Fedora 44 with Cinnamon 6.6.7. Unfortunately the 6.6-maintenance branch doesn't accept new features anymore and @leigh123linux suggested to make this PR against the master brunch.

Regarding the default <Alt><Super>Tab keyboard shortcut, I chose this one as the default for switching the active audio output device by one hand only and by something similar to the application switching, i.e. similar to <Alt>Tab.

P.S. Link to the YouTube video in the demonstration for those who liked it: www.youtube.com/watch?v=ky2rtCpbn7k

[github-actions]

Best-practices scanner

This is a regex-based check for API usage that can pose security, performance or
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This check is not perfect and will not replace a normal review.

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Found 1 potential issue(s):

⚠️ WARNING

⚠️ lang_bind

files/usr/share/cinnamon/applets/sound@cinnamon.org/applet.js:1116

Main.keybindingManager.addXletHotKey(this, "sound-cycle-output", this.cycleOutputKey, Lang.bind(this, this._cycleOutputDevice));

Lang.bind() is deprecated. Use arrow functions (() => {}) or Function.prototype.bind() instead.

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Automated pattern check.

[rostidev]

The above warning about use of the deprecated Lang.bind() is resolved in the amended commit.