`@xterm/addon-canvas` deprecated and will be removed in `@xterm/xterm` v6

[Venefilyn]

We currently rely on @xterm/addon-canvas for rendering the @xterm/xterm terminal. Once they release v6 however it will not be updated to work with it as it is currently deprecated in favor of the @xterm/addon-webgl.

Previously we chose Canvas over WebGL due to not being able to rely on browsers having WebGL enabled:

• terminal: update xterm dependency and start using an add on for the canvas #18157

We should evaluate enabling WebGL by default and having Canvas one as fallback. Currently AFAIK no features are added to the Canvas addon which means we cannot solve focus trapping Shift+Tab on #22504.