fix: apply class/style directives after attributes

[paoloricciuti]

Svelte 5 rewrite

Since the issue has come up multiple times and i didn't see much activity on #13338 (sorry @Rich-Harris if you were working on it) i took a shot at it. This PR make the test pass (i've also added the same logic for style attribute and directive since it also can be overridden by the directive. I've used the same technique that we use for the class and style directive of creating a derived for the function and change the value there. There's a bit of duplication which i don't particularly like but maybe it's better for readability.

Are there are better ways of doing this?

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[dummdidumm]

Good solution 👍 duplication is fine