Adjust logging to avoid expensive CosmosException.getMessage() diagnostics json serialization

[jaxpod70]

Description

Fixes excessive log line sizes in the ChangeFeedProcessor's partition processing loop caused by CosmosException.getMessage() serializing the full CosmosDiagnostics payload (request timelines, region contacts, retry history, metadata) into JSON when logged at WARN level.

Under heavy DB connection load, this produces multi-MB log lines (30+ MB observed) on every transient error (429 throttles, timeouts, connectivity issues) across all leased partitions concurrently. This causes log ingestion pipeline throttling/rejection, increased storage costs, and memory pressure from repeated serialization in a hot loop.

Fix: Split the existing log statement into two tiers in both epkversion.PartitionProcessorImpl and pkversion.PartitionProcessorImpl:

• WARN level: Uses CosmosException.getShortMessage() via parameterized logging — lightweight, no diagnostics payload
• DEBUG level: Logs the full exception (with diagnostics + stack trace) for deep troubleshooting when needed

This preserves observability for operators at default log levels while eliminating the excessive payload.

Related Issue

49320

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[github-actions]

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[jaxpod70]

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