Improve handling of webgl context loss

[Tyriar]

We should adopt xtermjs/xterm.js#3276. An easy fix is to just fallback when this happens, we need to make sure we don't save suggested renderer type if the webgl renderer is good though.

[connor4312]

Can you add verification steps?

[meganrogge]

To verify:

Context loss is achieved at a diff't limit for each computer.

Using VS code stable - create as many terminals as needed to trigger context loss. When you reach that state, you'll see

Now in Insider's, create the same number of terminals. You shouldn't see any of those context loss images.

[connor4312]

very nice, I like how the fallback magically works