fix: allow events to continue propagating following an error

[Rich-Harris]

This is an alternative to #11239. It's technically a breaking change, but I think the behaviour is much more reasonable than that of Svelte 4: if an event handler throws, propagation continues.

Fixes #8403. Demo

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[dummdidumm]

It's weird that the error is thrown only after all the events, and the last instead of the first error is thrown. Not sure which behavior is better, arguably two errors are even more of an edge case though.

[Rich-Harris]

It's not totally ideal, but we've gone from 'you only get one error' to 'you only get one error' — the fact that it's the last error rather than the first doesn't really make a colossal difference in my view. Similarly I don't think it matters that the error only 'happens' after the handlers have run, as long as the handlers themselves run in the right order. I'd 100% rather have this behaviour than the status quo