Added mapNotnull and maxOrNull to handle completedPipelineKeys in Pee…

[aman-agrawal]

Summary

Project Jira : Ref
Project Doc : NA

Issue : 6/42 TCs failing in orca-peering

java.util.NoSuchElementException
	at kotlin.collections.CollectionsKt___CollectionsKt.maxOrThrow(_Collections.kt:1916)
	at com.netflix.spinnaker.orca.peering.PeeringAgent.doMigrate$getLatestCompletedUpdatedTime(PeeringAgent.kt:258)
	at com.netflix.spinnaker.orca.peering.PeeringAgent.doMigrate(PeeringAgent.kt:280)
	at com.netflix.spinnaker.orca.peering.PeeringAgent.peerCompletedExecutions(PeeringAgent.kt:168)
	at com.netflix.spinnaker.orca.peering.PeeringAgentSpec.correctly computes the execution diff for completed #executionType(PeeringAgentSpec.groovy:91)

Solution : By using mapNotNull and maxOrNull, we ensure that the code gracefully handles the case when completedPipelineKeys is empty or when there are null values in the updated_at properties

How changes are verified

build successful & 42/42 TCs are passing in orca-peering

Documentation Updates

Do we need to update dashboards? No
Do we need to update SOP, new hire wiki or other documents? No

Rollback, Deployment Details

Can this change be rolled back automatically without any issue? Yes
Is this a backwards-compatible change in your opinion ? Yes
Pre deployment steps : NA
Post deployment steps : NA