Add jitter to retry logic in PartitionKeyResolver

[dkropachev]

Summary

• Add random jitter to exponential backoff delays to prevent thundering herd problem
• Improve retry reliability when multiple clients encounter failures simultaneously

Changes

• Add calculateJitteredDelay() method with ±20% random jitter
• Apply jitter to both DynamoDbException and general Exception retry paths
• Update log messages to show actual jittered delay values
• Ensure minimum 1ms delay after jitter calculation

Test plan

• Verify compilation passes
• Test that retry delays now include random jitter
• Confirm jitter is applied within expected range (±20%)
• Verify no behavioral changes to retry logic flow