fix: correctly match :has()'s selector during css pruning

[7nik]

Fixes #14072, alternative of #15207

:has() was matching only against descendants or siblings, but not sibling's descendants.

In this variant, I made apply_selector and related functions bidirectional. So the same logic can be applied to all selectors.
Changing the direction for selectors passed into :has() broke p:has(+ y) for the test has-with-render-tag and to fix it I added diving into the @render() tags during gathering siblings, which fixed the render-tag-loop test.

I also tried to cache the function retrieving neighbor elements and got the following cache hits rates on the test cases:
descendant_forward: 94,23%
descendant_backward: 55,91%
children_forward: 84,00%
children_backward: 33,51%
sibling_forward: 69,42%
sibling_backward: 59,94%
next_forward: 41,40%
next_backward: 2,44%
Though, I'm not sure how to measure performance change.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 6b71df2

The changes in this PR will be included in the next version bump.

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[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@15277

[dummdidumm]

Seriously impressive work. Thank you!

Feel free to open a separate PR with the cache, I can investigate a bit how much of a perf difference it makes.

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15277-svelte.vercel.app/

[7nik]

I was a bit busy and not sure how to properly benchmark, so eventually didn't get to it.