[Segment Replication] Create dummy test plugin to exercise custom codecs and add tests

[dreamer-89]

Is your feature request related to a problem? Please describe.
Coming as action item from bug #7781, add dummy plugin that provides custom codecs and add segment replication tests using this plugin. This is to mimic plugins such as k-NN, security-analytics which overrides CodecService. The intention is to ensure plugins which have custom codecs does not break with segment replication.

Describe the solution you'd like

1. Add a dummy plugin that overrides CodecService.
2. Add integration tests which verify that plugins overriding codecService works well with segment replication. Adding this plugin in tests would need some orchestration in tests, as tests today uses default codec service.

Describe alternatives you've considered

1. Add integration tests in dependent repos (k-NN e.g.)
   • Difficult to keep tests updated with changes on core
   • Not possible to keep up with new integrations.
2. Resort to manual test before release
   • Repeating duplicating work with every release
   • Error prone

Additional context
Add any other context or screenshots about the feature request here.