[server] Update remote log offsets before local segment cleanup

[loserwang1024]

Purpose

Linked issue: close #4247

Brief change log

Tests

API and Format

Documentation

[gyang94]

Here we checked the final state after updateRemoteLogEndOffset. It can't check whether we have the correct update processing order. We must 1) update copied watermark first then 2) delete local segment.
The problem is even if we first do operation 2 then 1, this test will also pass.

[loserwang1024]

t's hard to test this unless we add a hook before cleanupSegments, which is too intrusive to the production code.

[gyang94]

sure. It is not a blocker.

[gyang94]

@loserwang1024 would it be better to update remote log offset in one single function? (e.g. updateRemoteLogOffsets(start, end, highestCopied)). Now we have two functions updateRemoteLogStartOffset and updateRemoteLogEndOffset. But there is a hidden requirement is that we must call this two functions at the same time to update remote start/end offset together. Thus use one single function may be better.

This is not a blocker either, just a code optimization.