fix: widen ownership when calling setContext

[dummdidumm]

Instead of doing ownership addition at each getContext call site, we do it once as the setContext call site and make the state basically global.

• avoids potential false positives in edge cases
• makes the whole thing more performant, especially around things like calling getContext inside a list item component
• false negatives are unlikely from this (as shown by no current tests failing)

No new test added because this is mainly about performance.

fixes #15072

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🦋 Changeset detected

Latest commit: 8291cd9

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

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svelte	Patch

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Playground

pnpm add https://pkg.pr.new/svelte@15153