fix: the calculated columns explicit type convert into date

[zhaoyongjie]

SUMMARY

datetime column(grain columns) get default column type when this column lack of column type.

This situation occurs in the calculated columns.

related issue: #13702

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

make a calculated columns and selected is temporal checkbox

make calculated columns as time columns and do query.

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue: fixes Time filtering - Not working on calculated fields #13702
• 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 #14813 (0ed714e) into master (9a96dac) will decrease coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #14813      +/-   ##
==========================================
- Coverage   77.63%   77.39%   -0.24%     
==========================================
  Files         962      962              
  Lines       49156    49157       +1     
  Branches     6183     6183              
==========================================
- Hits        38161    38047     -114     
- Misses      10792    10907     +115     
  Partials      203      203              

Flag	Coverage Δ
hive	?
mysql	81.63% <100.00%> (+<0.01%)	⬆️
postgres	81.65% <100.00%> (+<0.01%)	⬆️
presto	?
python	81.73% <100.00%> (-0.44%)	⬇️
sqlite	81.27% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
superset/connectors/sqla/models.py	88.09% <100.00%> (-1.66%)	⬇️
superset/db_engines/hive.py	0.00% <0.00%> (-82.15%)	⬇️
superset/db_engine_specs/hive.py	70.32% <0.00%> (-17.08%)	⬇️
superset/db_engine_specs/presto.py	83.36% <0.00%> (-6.53%)	⬇️
superset/views/database/mixins.py	81.03% <0.00%> (-1.73%)	⬇️
superset/db_engine_specs/base.py	87.90% <0.00%> (-0.41%)	⬇️
superset/models/core.py	89.70% <0.00%> (-0.27%)	⬇️
superset/utils/core.py	88.91% <0.00%> (-0.13%)	⬇️

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[villebro]

As a workaround, I think this is a good default for now. However, in the long term it would be great if we could make it possible to sync the calculated column types, similar to how it's possible to sync the regular columns. This shouldn't be difficult to do - just trigger a query with a LIMIT of 1 and pick up the datatypes that come back from the database. However, let's leave that for a follow-up task.