fix: Timeseries visualization with Chart Source = Query

[hughhhh]

SUMMARY

Fix issue with running timeseries queries with chart source. Needed to create a new function get_timestamp_expression to handle dict vs. objects

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

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

[codecov]

Codecov Report

Merging #20795 (9b4a7ad) into master (81bd496) will decrease coverage by 11.47%.
The diff coverage is 55.26%.

❗ Current head 9b4a7ad differs from pull request most recent head 3d959af. Consider uploading reports for the commit 3d959af to get more accurate results

@@             Coverage Diff             @@
##           master   #20795       +/-   ##
===========================================
- Coverage   66.28%   54.81%   -11.48%     
===========================================
  Files        1756     1756               
  Lines       66756    66760        +4     
  Branches     7049     7059       +10     
===========================================
- Hits        44252    36594     -7658     
- Misses      20708    28368     +7660     
- Partials     1796     1798        +2     

Flag	Coverage Δ
hive	53.25% <46.61%> (+<0.01%)	⬆️
mysql	?
postgres	?
presto	53.11% <46.61%> (+<0.01%)	⬆️
python	57.81% <46.61%> (-23.70%)	⬇️
sqlite	?
unit	50.25% <43.22%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...d/packages/superset-ui-chart-controls/src/types.ts	100.00% <ø> (ø)
...ackages/superset-ui-core/src/query/types/Column.ts	100.00% <ø> (ø)
...s/legacy-plugin-chart-heatmap/src/controlPanel.tsx	57.14% <ø> (ø)
.../plugin-chart-echarts/src/MixedTimeseries/index.ts	25.00% <ø> (ø)
...ins/plugin-chart-echarts/src/components/Echart.tsx	0.00% <0.00%> (ø)
...rset-frontend/src/components/Chart/chartReducer.ts	25.00% <0.00%> (ø)
...t-frontend/src/dashboard/actions/dashboardState.js	37.05% <ø> (+0.50%)	⬆️
...rset-frontend/src/dashboard/actions/datasources.ts	0.00% <0.00%> (ø)
...frontend/src/dashboard/components/Header/index.jsx	59.39% <ø> (ø)
...board/components/nativeFilters/FilterBar/index.tsx	60.58% <ø> (ø)
... and 341 more

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[AAfghahi]

does this need the variable declaration that the below function has?

[AAfghahi]

same question here.