Fix/batch backfill v18

[DavidWeiss2]

Change Summary

The current batch mechanism is failing on Firestore big collections with a function crash. This PR fixing this issue.

Also on this PR - Better comments for failing batch (the current one get trimmed when multiple errors)

but for v18

PR Checklist

• [x] I have read and signed the Contributor License Agreement.

[DavidWeiss2]

Saw the conflicts, fixing them.

[DavidWeiss2]

@jasonbosco Conflict resolved