fix value extraction from JSON in source comprehensive test

[subodh1810]

Issue : #5380
In the PR #4457 we made changes to the class SourceComprehensiveTest, specifically on how we extract values from JSON record. This worked for Bigquery but broke the test for other sources like mssql, postgres, etc.

Portion of this was fixed in #5370

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[subodh1810]

/test connector=source-mysql

🕑 source-mysql https://github.com/airbytehq/airbyte/actions/runs/1125311151
✅ source-mysql https://github.com/airbytehq/airbyte/actions/runs/1125311151

[subodh1810]

/test connector=source-mssql

🕑 source-mssql https://github.com/airbytehq/airbyte/actions/runs/1125313047
✅ source-mssql https://github.com/airbytehq/airbyte/actions/runs/1125313047

[subodh1810]

/test connector=source-snowflake

🕑 source-snowflake https://github.com/airbytehq/airbyte/actions/runs/1125313654
✅ source-snowflake https://github.com/airbytehq/airbyte/actions/runs/1125313654

[subodh1810]

/test connector=source-bigquery

🕑 source-bigquery https://github.com/airbytehq/airbyte/actions/runs/1125313865
✅ source-bigquery https://github.com/airbytehq/airbyte/actions/runs/1125313865

[subodh1810]

/test connector=source-cockroachdb

🕑 source-cockroachdb https://github.com/airbytehq/airbyte/actions/runs/1125316668
✅ source-cockroachdb https://github.com/airbytehq/airbyte/actions/runs/1125316668

[subodh1810]

/test connector=source-db2

🕑 source-db2 https://github.com/airbytehq/airbyte/actions/runs/1125316869
✅ source-db2 https://github.com/airbytehq/airbyte/actions/runs/1125316869

[subodh1810]

/test connector=source-oracle

🕑 source-oracle https://github.com/airbytehq/airbyte/actions/runs/1125318151
✅ source-oracle https://github.com/airbytehq/airbyte/actions/runs/1125318151