fix: restore batch along with effect context

[Rich-Harris]

Partial alternative to #16621. That PR is doing more than this one (it addresses a memory leak that this PR doesn't touch) but I don't trust the get_batch logic and so I wanted to see if it was as straightforward as restoring the batch when we restore the effect context, which feels like the correct fix.

This works — we just also need to deactivate the batch when a component unsuspends, in the case that it's inside a pending boundary (otherwise it would already deactivate)

Fixes #16596
Fixes sveltejs/kit#14124

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Playground

pnpm add https://pkg.pr.new/svelte@16668