Better logging on empty topics

[bcarter97]

Description

Currently we log Not loading data from empty topic if the lowest offset isn't <= the highest offset. This doesn't necessarily mean it's empty, but could instead mean messages have been deleted and the highest offset is > 0.

Additionally added some debug logging to show what offsets are deemed empty or not.

Example DEBUG logs from test

08:29:55.590 [io-compute-2] DEBUG u.s.f.kafka.topicloader.TopicLoader - Assigning partitions: load-state-topic-1-0,load-state-topic-1-1,load-state-topic-2-0,load-state-topic-2-1
08:29:55.642 [io-compute-4] DEBUG u.s.f.kafka.topicloader.TopicLoader - Seeking to offset 0 for partition load-state-topic-1-0
08:29:55.642 [io-compute-2] DEBUG u.s.f.kafka.topicloader.TopicLoader - Seeking to offset 0 for partition load-state-topic-1-1
08:29:55.642 [io-compute-7] DEBUG u.s.f.kafka.topicloader.TopicLoader - Seeking to offset 0 for partition load-state-topic-2-0
08:29:55.642 [io-compute-6] DEBUG u.s.f.kafka.topicloader.TopicLoader - Seeking to offset 0 for partition load-state-topic-2-1
08:29:55.643 [io-compute-6] DEBUG u.s.f.kafka.topicloader.TopicLoader - Non-empty offsets: (load-state-topic-1-0,LogOffset(highest=10, lowest=0)), (load-state-topic-1-1,LogOffset(highest=5, lowest=0))
08:29:55.643 [io-compute-6] DEBUG u.s.f.kafka.topicloader.TopicLoader - Empty offsets: (load-state-topic-2-0,LogOffset(highest=0, lowest=0)), (load-state-topic-2-1,LogOffset(highest=0, lowest=0))
08:29:55.643 [io-compute-6] INFO  u.s.f.kafka.topicloader.TopicLoader - Not loading data from load-state-topic-2-0 as lowest offset 0 <= highest offset 0
08:29:55.643 [io-compute-6] INFO  u.s.f.kafka.topicloader.TopicLoader - Not loading data from load-state-topic-2-1 as lowest offset 0 <= highest offset 0
08:29:56.876 [io-compute-4] INFO  u.s.f.kafka.topicloader.TopicLoader - Finished loading data from load-state-topic-1-1 at offset 4
08:29:57.981 [io-compute-9] INFO  u.s.f.kafka.topicloader.TopicLoader - Finished loading data from load-state-topic-1-0 at offset 9

Related Issues

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Definition of Done:

The Below tasks should be completed before marking a PR as ready for review.

• Added / Removed / Updated relevant tests
• Scaladoc updated