Group same failed queries together in keys's output

[frouioui]

This PR groups query that failed multiple times into a single JSON element instead of repeating the same query/failure.

"failed": [
      {
        "query": "I am a failing query;",
        "lineNumbers": [
          463,
          781
        ],
        "error": "syntax error at position 2 near 'I'"
      }
    ]

## Failures
|Query|Error|Count|
|---|---|---|
|I am a failing query;|syntax error at position 2 near 'I'|2|