fix: Handle Python date format for GENERIC_CHART_AXES feature

[john-bodley]

SUMMARY

Fixes #25134.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

BEFORE

SELECT date_trunc('day', CAST(epoch_s AS TIMESTAMP)) AS epoch_s,
       COUNT(*) AS count
FROM
  (SELECT 123 AS epoch_s,
          12300 AS epoch_ms,
          '2023-01-01' AS ds) AS virtual_table
GROUP BY date_trunc('day', CAST(epoch_s AS TIMESTAMP))
ORDER BY count DESC
LIMIT 1000;

AFTER

SELECT date_trunc('day', CAST(from_unixtime(epoch_s) AS TIMESTAMP)) AS epoch_s,
       COUNT(*) AS count
FROM
  (SELECT 123 AS epoch_s,
          12300 AS epoch_ms,
          '2023-01-01' AS ds) AS virtual_table
GROUP BY date_trunc('day', CAST(from_unixtime(epoch_s) AS TIMESTAMP))
ORDER BY count DESC
LIMIT 1000;

TESTING INSTRUCTIONS

Tested locally. Regrettably there's currently no unit testing for the entire adhoc_column_to_sqla function.

ADDITIONAL INFORMATION

• Has associated issue: epoch_s columns not converted to timestamps correctly in 3.0.0rc3  #25134
• 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

[michael-s-molina]

LGTM