auto-set 'Is Temporal' to true where column_name == '__time'

[mistercrunch]

closes #6853

[codecov-io]

Codecov Report

Merging #6857 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #6857      +/-   ##
==========================================
+ Coverage   64.76%   64.78%   +0.01%     
==========================================
  Files         421      421              
  Lines       20384    20393       +9     
  Branches     2249     2249              
==========================================
+ Hits        13202    13211       +9     
  Misses       7049     7049              
  Partials      133      133

Impacted Files	Coverage Δ
superset/db_engine_specs.py	57.03% <100%> (+0.27%)	⬆️
superset/connectors/sqla/models.py	81.86% <100%> (+0.06%)	⬆️
superset/assets/src/chart/chartAction.js	45.23% <0%> (ø)	⬆️
superset/views/core.py	74.94% <0%> (+0.03%)	⬆️

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[john-bodley]

@mistercrunch that could be a good idea. According to the Druid SQL docs __time seems to be the only implicit time column.

[mistercrunch]

@john-bodley I integrated your comments