HDDS-6426. OM keyTable and fileTable use different key formats.

[JyotinderSingh]

What changes were proposed in this pull request?

HDDS-5835 changed OMMetadataManager#getKeyTable to return a different table based on the bucket layout: fileTable for FSO buckets, keyTable otherwise. The problem is that these two tables have completely different sets of keys and key formats. It is not enough to change existing requests expecting to operate on the key table to now point to the file table if they are invoked on an FSO bucket, because they will query the table with the wrong key format.

This implementation is misleading for developers (you ask for a keyTable and might get a fileTable instead) and caused HDDS-6414, while possibly masking other similar bugs for existing requests.

This patch introduces a new interface to define methods to build DB Keys to query entries inside the keyTable and fileTable. We introduce two implementations of this interface - one for FSO, and another for OBS/LEGACY.
This should reduce the effort on developer side to handle key generation logic while writing new Request classes or tests.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-6426

How was this patch tested?

Related unit tests

[kerneltime]

Closing this PR as it has not had any activity in a long time, we need to revisit this Jira and redo this PR.