Report reingestion errors in aggregate (#4074)

* Add is_reingestion context to Ingester class

* Revert "Add is_reingestion context to Ingester class"

This reverts commit dd86d9e.

* Do not report to Slack during pull_data task for reingestion, but in aggregate task

* Fix formatting

* Make log links more compact

* Report at most 5 failed task logs

Author: stacimc