fix: handle member expressions in directives

[navorite]

tried some more edge cases as well, this should match svelte 4's behaviour.

honestly, this would have been better if this was done this at the AST level but this isn't needed if stores are gonna be removed/deprecated in svelte 6 ( i believe? ) anyways.

closes #10566

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[Rich-Harris]

to be fair it's not just stores, you can also just do use:foo.bar.baz. But I think this solution is Good Enough™ for what it's used for. thanks!