Extension API: Provide the option for Code Lenses to be stacked vertically in the margin

[StanFromTraction]

Hey,

I use Copilot Lab's Brushes extension. It's amazing, but since the lenses are quite tall and keep popping up whenever you select text or a function, they cause the editor to vertically shift.

Not only is it visually jarring, but it also "breaks" code selection; you must either predict the shift or wait for it to happen to reposition your cursor and avoid selecting the wrong lines.

Since the left margin is mostly empty (with a few edge cases like the Code Actions icon), it makes sense for the lenses to appear vertically stacked in the margin. That way they don't interfere.

[gjsjohnmurray]

Related to #90235

[roblourens]

Thanks @gjsjohnmurray, I will close it as a dupe of that for some alternate rendering