fix(elasticsearch logging): log how long bulk execution took

[darnaut]

Elasticsearch bulk execution logs currently always print Took time ms as -1:

INFO  c.l.m.s.e.update.BulkListener:51 - Successfully fed bulk request. Number of events: 5 Took time ms: -1

The problem is that the printed time is actually the bulk ingest preprocessing time, which is -1 if ingest is not enabled.

This change now logs how long bulk execution took. The bulk ingest preprocessing time is only logged if available.

INFO  c.l.m.s.e.update.BulkListener - Successfully fed bulk request. Number of events: 12 Took time ms: 542

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub