Reset the consumer offsets for a table actively ingesting

Usecase: Realtime table where the consumer starts lagging behind (say 3-4 hours). User wished to reset the consumer offsets to latest. They were okay with losing data of the last 3-4 hours.

The issue names no files, tests, or entry points. Start by tracing Pinot’s realtime table consumer-offset handling and clarify how a reset-to-latest operation should behave while ingestion continues. Done means the behavior is defined and the reported data-loss case is covered by appropriate tests.

Written by the indexing model from the issue text.