CBG-4549: Refactor resync Init so the reason for a reset is always logged

[bbrks]

CBG-4549

• Refactor resync Init so the reason for a reset is always logged.
  Scenarios covered by subtests in TestResyncDCPInit:

Initialize_new_run_with_empty_cluster_state db:db Resync: Resetting resync process with ID: "..." - no previous run found
Reinitialize_existing_run db:db Resync: Resuming resync with ID: "..."
Reinitialize_completed_run db:db Resync: Resetting resync process with ID: "..." - previous run completed
Force_restart_existing_run db:db Resync: Resetting resync process with ID: "..." - reset option requested

• Remove outdated resync information (since 3.0 we have cluster-aware resync which won't allow multiple nodes to run resync concurrently)

Integration Tests

• GSI=true,xattrs=true https://jenkins.sgwdev.com/job/SyncGateway-Integration/2985/

[github-actions]

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[torcolvin]

I am fine with this change but I wonder if the two common scenarios here actually should not have the log line reset? I am not convinced by this, but I worry reset implies dropping previous bad state.

clusterStatus == nil - technically this is a reset because you are "setting" but I think that this is better stated as just "Starting resync process".

Similarly with statusDoc.State == BackgroundProcessStateCompleted but this case I can see how reset seems like the right word.