fix: properly validate snippet/slot interop

[dummdidumm]

The previous validation for checking if slots with let directives were rendered with {@render children(...)} had false positives

• threw an error even if the other side didn't make use of the arguments, i.e. wasn't actually using a let directive
• didn't check that the rendered snippet actually was the children property

This fixes the validation by only applying it to children render tags, and by adding the slot to $$slots.default instead of $$props.children in more cases (when it's using <svelte:fragment> or let: directives, which both mean you're using old slot syntax)

Fixes #12414

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🦋 Changeset detected

Latest commit: 01683b4

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

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[diazmartinx]

I have been having this problem that I think is related to {@render ...}
My codebase works perfectly on v175 but breaks on v183 & v182 too.

The error: "Uncaught (in promise) DOMException: Failed to execute 'appendChild' on 'Node': This node type does not support this method."

This just happens when the project is builded, not in dev

[ixxie]

I have been having this problem that I think is related to {@render ...} My codebase works perfectly on v175 but breaks on v183 & v182 too.

The error: "Uncaught (in promise) DOMException: Failed to execute 'appendChild' on 'Node': This node type does not support this method."

This just happens when the project is builded, not in dev

Probably related to #12422