fix: take snippets into account when scoping CSS

[dummdidumm]

Updated and finalized version of #10208.

The approach is to collect all render tags, then for each render tag both traverse up the elements and cut selectors from the end, until either no options left or a match is found. The assumption behind this is that the contents of the render tag would complete the selector.

There are ways to make this more strict (cutting a selector from the end only if the combinator still can match afterwards, check if we have snippets in the component and where they are rendered, etc), but the result will only mean more things pruned potentially, but no false negatives, so this is a good first iteration IMO.

Ideally merged after #13567/#13568 since it will result in some merge conflicts and this PR is far simpler to resolve the conflicts within

fixes #10143

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[trueadm]

Can't we traverse backwards through the selectors?

[dummdidumm]

Wdym? We're traversing them back to front. That's what the rest of the pruning algorithm does.

[trueadm]

I mean a for loop with negative index rather copying the array and popping each item

[dummdidumm]

The result of pop isn't passed to anything, the resulting array that is one item less afterwards is. Looping with negative index wouldn't change the fact that we have to create a new array, if that's what you're concerned about (in fact we would have to create more since we'd have to do it for each iteration of the inner loop, rather of only each iteration of the outer loop)