Defensively guard against invalid connections

[cmgrote]

Note

Add support for capturing metric details in external DQ test run history and update tests across assets to populate it.

• Models:
  • Add AssetExternalDQTestMetric and assetExternalDQTestMetricInfo on AssetExternalDQTestRunHistory for observed/upper/lower bounds.
• Tests:
  • Update numerous asset tests to include assetExternalDQTestMetricInfo in external DQ test run builders.

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