Fix(api): loading viz_type from request params

[hdahme]

SUMMARY

Previously, when passing viz_type via the API, it would default to table. This change allows us to send viz_type and have the charts respect it in the UI

TESTING INSTRUCTIONS

Make an API request via python and send the following params

params = {
        "viz_type": "big_number",
        "groupby": columns,
        "metrics": metrics,
        "adhoc_filters": [
            {
                "expressionType": "SQL",
                "sqlExpression": where_clause,
                "clause": "WHERE",
            }
        ]
    }

The resulting chart would always be a table. No longer

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

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[korbit-ai]

I was unable to post the issues I found. This could be because a force push or squash has changed the commit history since I scanned this pull request. You can get another review by commenting /korbit-review.