feat: add writeUpsert util to localstorage collection

[LuggaPugga]

🎯 Changes

This PR adds a writeUpsert utility to the localstorage collection, inspired by the upsert utility in the query collection
Feel free to let me know if you'd like any changes

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm test.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

[changeset-bot]

🦋 Changeset detected

Latest commit: 9e5dc2f

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

This PR includes changesets to release 14 packages

Name	Type
@tanstack/db	Minor
@tanstack/angular-db	Patch
@tanstack/electric-db-collection	Patch
@tanstack/offline-transactions	Patch
@tanstack/powersync-db-collection	Patch
@tanstack/query-db-collection	Patch
@tanstack/react-db	Patch
@tanstack/rxdb-db-collection	Patch
@tanstack/solid-db	Patch
@tanstack/svelte-db	Patch
@tanstack/trailbase-db-collection	Patch
@tanstack/vue-db	Patch
todos	Patch
@tanstack/db-example-paced-mutations-demo	Patch

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