[Segment Replication] Merge to main tracking - Refactoring of existing classes to support segrep.

[mch2]

This is a tracking task for the refactoring tasks outlined in our meta merging issue.

• Move RecoveryIndex to top level class and move inner classes from RecoveryIndex
• Move RecoveryState.Timer to top level
• Change GatedAutoCloseable to AutoCloseableRefCounted
• Create base class ReplicationTarget and refactor RecoveryTarget to inherit from it.
• Engine interface changes for addIndexOperationToTranslog and addDeleteOperationToTranslog

[kartg]

Move RecoveryIndex to top level class and move inner classes from RecoveryIndex
Move RecoveryState.Timer to top level
Change GatedAutoCloseable to AutoCloseableRefCounted

I can pick these up

[kartg]

Move RecoveryState.Timer to top level
Change GatedAutoCloseable to AutoCloseableRefCounted

PR - #2965

[kartg]

Move RecoveryIndex to top level class and move inner classes from RecoveryIndex

PR - #3075