fix: remove memory leak, make beforeUpdate etc work correctly

[Rich-Harris]

Fixes #10548. We were pushing signals to an array on the component context so that beforeUpdate/afterUpdate callbacks could observe them, but we were never cleaning this array up.

It turns out we only need to create this array for non-runes components, since beforeUpdate/afterUpdate are forbidden in runes mode. We can therefore do the binding inside mutable_source. We don't need to do any additional cleanup work because the context should be garbage collected when the component is destroyed.

I also realised that in the (vanishingly rare!) case that a runes-mode component is passing proxied state into a non-runes-mode component, which has a beforeUpdate/afterUpdate callback, the callbacks do not run when a property of the proxied state is updated. This is fixed in this PR by using deep_read instead of shallowly reading props.

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Latest commit: 9838ddf

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

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