perf: don't use tracing overeager during dev

[dummdidumm]

#17176 is a case where many sources are created and then written to (due to Svelte 4 prop mechanics), and our tracing kicked in eagerly. That combined with the excessive depth of the related stack traces slowed things down tremendously.

The fix is simple: Don't record stack traces until we've seen this source get updated for a couple of times. Additionally we now delete the updates map after a flush. Previously it was just an ever-growing stack trace map.

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[changeset-bot]

🦋 Changeset detected

Latest commit: efb49d2

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

This PR includes changesets to release 1 package

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svelte	Patch

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Playground

pnpm add https://pkg.pr.new/svelte@17183

[Rich-Harris]

clever!