[mongo] include explain operations in samples

[lu-zhengda]

What does this PR do?

This PR adds support for capturing explain operations in MongoDB activity samples.

Motivation

Previously, explain operations were excluded from activity samples, which could result in an incomplete count of active database operations. Including them ensures more accurate tracking and representation of database activity.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.32%. Comparing base (bfbd8a7) to head (4c1ad4a).
Report is 8 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
hive	?
hivemq	?
ignite	?
jboss_wildfly	?
kafka	?
mongo	93.07% <ø> (-0.73%)	⬇️
presto	?
solr	?

Flags with carried forward coverage won't be shown. Click here to find out more.