[8.0] Elasticsearch generateDocs: remove multiplication in timestamp when committing to monitoring

[rupozzi]

This is a way to resolve #5320 without going to the ES backend and manipulate old indices.
Very simply, let us make sure that when a record is added to ES, it already has a timestamp in milliseconds, and skip the whole multiplication process when committing it.

BEGINRELEASENOTES

*Monitoring
FIX: Removing multiplication in timestamp when committing to monitoring

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[rupozzi]

Another topic worth discussing brought up by @chaen in #5320 would be also whether we should even add a timestamp at all when committing the records, when we could instead add it directly when adding the record.