Feat/add on message drop in events plugin

[VivekPipaliya23]

Proposed Changes

This PR will send message being dropped from the queue due to various reasons to events sidecar.
It will introduce on_message_drop hook in vmq_events_sidecar plugin.

Types of Changes

• Bugfix (non-breaking change which fixes issue #XXXX)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (correction or otherwise)
• Cosmetics (whitespace, styles...)
• DevOps (Build scripts, pipelines...)

Checklist

• I have read the CODE_OF_CONDUCT.md document
• All tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if needed)
• Any dependent changes have been merged and published in related repositories
• I have updated changelog (At the bottom of the release version)
• I have squashed all my commits into one before merging

[dhruvjain99]

Two minor comments. Rest looks fine to me.