MM2 High-Resolution Offset Translation

The current OffsetSyncStore implementation https://github.com/apache/kafka/blob/8b72a2c72f09838fdd2e7416c98d30fe876b4078/connect/mirror/src/main/java/org/apache/kafka/connect/mirror/OffsetSyncStore.java#L57 stores a sparse index of offset syncs. This attempts to strike a balanced default behavior between offset translation availability, memory usage, and throughput on the offset syncs topic.

However, this balanced default behavior is not good enough in all circumstances. When precise offset translation is needed away from the end of the topic, such as for consumer groups with persistent lag, offset translation can be more precise. Users should have a way to configure high-precision offset translation, either through additional memory usage or re-reading the offset syncs topic.