refactor: decouple pandas postprocessing operator

[zhaoyongjie]

SUMMARY

Currently, Superset use a single module maintained postprocessing operator. This PR ONLY split the original single module into multiple modules.

TESTING INSTRUCTIONS

Python unit test.

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 #18710 (103baa1) into master (324a15d) will decrease coverage by 0.01%.
The diff coverage is 88.80%.

❗ Current head 103baa1 differs from pull request most recent head 1df183e. Consider uploading reports for the commit 1df183e to get more accurate results

@@            Coverage Diff             @@
##           master   #18710      +/-   ##
==========================================
- Coverage   66.28%   66.26%   -0.02%     
==========================================
  Files        1605     1619      +14     
  Lines       62863    62939      +76     
  Branches     6341     6341              
==========================================
+ Hits        41666    41706      +40     
- Misses      19545    19581      +36     
  Partials     1652     1652              

Flag	Coverage Δ
hive	52.26% <32.56%> (+0.11%)	⬆️
mysql	81.37% <88.80%> (+0.04%)	⬆️
postgres	81.42% <88.80%> (+0.04%)	⬆️
presto	?
python	81.74% <88.80%> (-0.08%)	⬇️
sqlite	81.11% <88.80%> (+0.04%)	⬆️

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

Impacted Files	Coverage Δ
superset/utils/pandas_postprocessing/prophet.py	54.38% <54.38%> (ø)
superset/utils/pandas_postprocessing/geography.py	82.85% <82.85%> (ø)
superset/utils/pandas_postprocessing/compare.py	88.88% <88.88%> (ø)
superset/utils/pandas_postprocessing/aggregate.py	90.90% <90.90%> (ø)
superset/utils/pandas_postprocessing/pivot.py	91.17% <91.17%> (ø)
superset/utils/pandas_postprocessing/rolling.py	92.50% <92.50%> (ø)
superset/utils/pandas_postprocessing/utils.py	95.83% <95.83%> (ø)
superset/utils/pandas_postprocessing/__init__.py	100.00% <100.00%> (ø)
superset/utils/pandas_postprocessing/boxplot.py	100.00% <100.00%> (ø)
...perset/utils/pandas_postprocessing/contribution.py	100.00% <100.00%> (ø)
... and 8 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 324a15d...1df183e. Read the comment docs.

[villebro]

This is great, much more manageable!

[1c7]

老哥有兴趣交流下不？我们最近也在用 Superset 和 ClickHouse 搭建自己内部的数据项目，我微信 agoodob