This is a followup fixes related to #105298
This PR adds shortcuts to toggle the sidebar, toolbar, channels and
other regions across various editors with the Ctrl-LeftBracket &
Ctrl-RightBracket shortcuts.
An additional shortcut to toggle the Asset Shelf in the 3D Viewport via
Shift Spacebar was also added. This shortcut will be important for
various workflows in the future.
To avoid shortcut conflicts and improve consistency, Ctrl-L is now
consistently being used for select_linked operations.
Ref !112042.
a0e5b03126