fix(explore): refine previous calendar range

[zhaoyongjie]

SUMMARY

fix #12283
refine previous calendar range in new timepicker

for example:
current date is: 2021-01-06

previous calendar week == 2020-12-28 ≤ col < 2021-01-04
previous calendar month == 2020-12-01 ≤ col < 2021-01-01
previous calendar year == 2020-01-01 ≤ col < 2021-01-01

TEST PLAN

changed UT

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-io]

Codecov Report

Merging #12308 (cbf241c) into master (1f83472) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #12308      +/-   ##
==========================================
- Coverage   67.15%   67.09%   -0.06%     
==========================================
  Files        1002     1002              
  Lines       49300    49300              
  Branches     5010     5010              
==========================================
- Hits        33106    33080      -26     
- Misses      16069    16095      +26     
  Partials      125      125              

Flag	Coverage Δ
cypress	51.43% <ø> (ø)
javascript	61.20% <ø> (ø)
python	64.08% <100.00%> (-0.10%)	⬇️

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

Impacted Files	Coverage Δ
superset/utils/core.py	89.87% <100.00%> (-0.35%)	⬇️
superset/db_engine_specs/mysql.py	79.59% <0.00%> (-12.25%)	⬇️
superset/db_engine_specs/sqlite.py	65.62% <0.00%> (-9.38%)	⬇️
superset/utils/celery.py	96.42% <0.00%> (-3.58%)	⬇️
superset/result_set.py	96.69% <0.00%> (-1.66%)	⬇️
superset/models/core.py	88.04% <0.00%> (-0.82%)	⬇️
superset/views/core.py	74.92% <0.00%> (-0.46%)	⬇️
superset/connectors/sqla/models.py	91.24% <0.00%> (-0.27%)	⬇️
superset/db_engine_specs/base.py	85.82% <0.00%> (-0.26%)	⬇️
... and 2 more

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[graceguo-supercat]

LGTM!
unit test is great. Thanks so much!

[ktmud]

LGTM. The code is much cleaner this way!