Revert translog changes introduced for CCR

[dnhatn]

We introduced these changes in #26708 because for CCR.
However, CCR now uses Lucene instead of translog.

This commit reverts these changes so that we can
minimize differences between the ccr and the master branch.

[elasticmachine]

Pinging @elastic/es-distributed

[martijnvg]

Thanks for removing this now redundant code. LGTM

[martijnvg]

The PR CI failed because of:

java.lang.AssertionError: seqNo [419] was processed twice in generation [2], with different data. prvOp [Index{id='usxLh2QBIuRTcPeFc2TS', type='doc', seqNo=419, primaryTerm=2, version=1, versionType=EXTERNAL, autoGeneratedIdTimestamp=-1}], newOp [Index{id='usxLh2QBIuRTcPeFc2TS', type='doc', seqNo=419, primaryTerm=1, version=1, versionType=EXTERNAL, autoGeneratedIdTimestamp=-1}]
  2>    at __randomizedtesting.SeedInfo.seed([86E02CAB8502E91F]:0)
  2>    at org.elasticsearch.index.translog.TranslogWriter.assertNoSeqNumberConflict(TranslogWriter.java:227)
  2>    at org.elasticsearch.index.translog.TranslogWriter.add(TranslogWriter.java:193)
  2>    at org.elasticsearch.index.translog.Translog.add(Translog.java:497)
  2>    at org.elasticsearch.index.engine.InternalEngine.index(InternalEngine.java:859)
  2>    at org.elasticsearch.index.shard.IndexShard.index(IndexShard.java:709)
  2>    at org.elasticsearch.index.shard.IndexShard.applyIndexOperation(IndexShard.java:685)
  2>    at org.elasticsearch.index.shard.IndexShard.applyTranslogOperation(IndexShard.java:1215)
  2>    at org.elasticsearch.indices.recovery.RecoveryTarget.indexTranslogOperations(RecoveryTarget.java:397)
  2>    at org.elasticsearch.indices.recovery.PeerRecoveryTargetService$TranslogOperationsRequestHandler.messageReceived(PeerRecoveryTargetService.java:458)
  2>    at org.elasticsearch.indices.recovery.PeerRecoveryTargetService$TranslogOperationsRequestHandler.messageReceived(PeerRecoveryTargetService.java:448)
  2>    at org.elasticsearch.transport.RequestHandlerRegistry.processMessageReceived(RequestHandlerRegistry.java:63)
  2>    at org.elasticsearch.transport.TcpTransport$RequestHandler.doRun(TcpTransport.java:1679)

I don't think it is related to the changes in this PR, but I thought changes were made so that this assertion wouldn't trigger?

[dnhatn]

I've relaxed versionType and timestamp. This test failed because the primary terms were different.

prvOp [Index{id='usxLh2QBIuRTcPeFc2TS', type='doc', seqNo=419, primaryTerm=2, version=1, versionType=EXTERNAL, autoGeneratedIdTimestamp=-1}],

newOp [Index{id='usxLh2QBIuRTcPeFc2TS', type='doc', seqNo=419, primaryTerm=1, version=1, versionType=EXTERNAL, autoGeneratedIdTimestamp=-1}]

[dnhatn]

@elasticmachine test this please

[dnhatn]

Thanks @martijnvg for reviewing.