Do not set ending sequence number for child shard partitions discovered after initial scan for shards

[graytaylor0]

Description

This change fixes a potential data loss scenario where shards can be skipped completely on this condition in ShardConsumer (

data-prepper/data-prepper-plugins/dynamodb-source/src/main/java/org/opensearch/dataprepper/plugins/source/dynamodb/stream/ShardConsumer.java

Line 410 in 4b4febc

LOG.info("LastShardIterator is provided, but there is no Last Event Time, skip processing");

). This data loss can happen if the partitions for the shards are created in source coordination after the shard has already closed (in the case that a child shard is already closed by the time data prepper fully processes the parent shard).

Check List

• New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
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