fix(file-provider): Make change batch delivery idempotent

[claucambra]

Resolves

Possible explanation for #10647

Summary

The current change delivery batch design is not idempotent. In practice this means that it is possible for change delivery batches to not be correctly processed by the sync engine, causing certain changes to not be correctly delivered to the File Provider framework.

Specifically, the current design automatically advances the change delivery state before said change batch is delivered to the File Provider framework; if the File Provider extension process is closed/crashes before the File Provider framework has processed the batch, this same batch will never be provided again to the framework and will be skipped, preventing certain changes from being delivered.

This PR addresses this by only advancing the change delivery state once the current batch is recognised as processed by the File Provider framework

Checklist

• Sign-off message is added to all commits.
• The commit messages are following The Conventional Commits specification.
• The commit history is clean with no merge commits.
  • How to rebase your commits
  • How to squash commits with rebase
• Uploaded screenshots from before and after for UI changes.
• Test(s) added to branch, with before/after results included in PR description, for performance improvements where applicable.
• Documentation has been updated or is not required.
• Backports requested where applicable (critical bugfixes).
• Labels added where applicable (bug/enhancement).
• Milestone added for target version.

AI (if applicable)

• The content of this PR was partly or fully generated using AI
  • I have read the guidelines for AI-assisted contributions.
  • I have read Nextcloud's AI Contribution Policy.

[claucambra]

/backport to stable-34.0

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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