fix: V1ConfigurationMapper - return empty list for null Dimensions to prevent ArgumentNullException

[Krishna-Chaitanya4]

Summary

Fixes a regression introduced in PR #2740 where the V1ConfigurationMapper returns null for AzureMetricConfiguration.Dimensions when the source has no dimensions configured. The AzureMetricConfigurationValidator calls .Any() on this property, which throws ArgumentNullException when it is null.

Root Cause

AutoMapper defaulted null collections to empty lists. The hand-written mapper preserved null, but downstream validators expect non-null collections.

Error

System.ArgumentNullException: Value cannot be null. (Parameter 'source') at System.Linq.Enumerable.Any[TSource](IEnumerable source) at AzureMetricConfigurationValidator.ValidateAzureMetricConfiguration(line 58)

Fix

`diff

• Dimensions = source.Dimensions?.Select(MapMetricDimension).ToList(),

• Dimensions = source.Dimensions?.Select(MapMetricDimension).ToList() ?? new List(),
  `

Verification

• Build: 0 errors, 0 warnings
• Unit tests: 1542 passed, 0 failed

[github-actions]

Thank you for your contribution! 🙏 We will review it as soon as possible.

[Krishna-Chaitanya4]

/azp run

[azure-pipelines]

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