API: Remove CalendarDay

[mroeschke]

• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff

Given that we want to ship 0.24.0 soon and that converting 'D' and Day to always act as calendar day warrants more game-planning, this PR just simply removes CalendarDay and reverts 'D' and Day to their prior behavior.

[pep8speaks]

Hello @mroeschke! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/arrays/datetimes.py !

• There are no PEP8 issues in the file pandas/core/resample.py !

• There are no PEP8 issues in the file pandas/tests/indexes/datetimes/test_date_range.py !

• There are no PEP8 issues in the file pandas/tests/indexes/datetimes/test_timezones.py !

• There are no PEP8 issues in the file pandas/tests/indexes/timedeltas/test_timedelta_range.py !

• There are no PEP8 issues in the file pandas/tests/resample/test_datetime_index.py !

• There are no PEP8 issues in the file pandas/tests/resample/test_period_index.py !

• There are no PEP8 issues in the file pandas/tests/series/test_timezones.py !

• There are no PEP8 issues in the file pandas/tests/tseries/offsets/test_offsets.py !

• There are no PEP8 issues in the file pandas/tests/tseries/offsets/test_ticks.py !

• There are no PEP8 issues in the file pandas/tseries/offsets.py !

[mroeschke]

This is not needed AFAICT. All internal calls to this method have Timestamp inputs.

[codecov]

Codecov Report

Merging #24330 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24330      +/-   ##
==========================================
+ Coverage   92.28%   92.28%   +<.01%     
==========================================
  Files         162      162              
  Lines       51831    51813      -18     
==========================================
- Hits        47830    47816      -14     
+ Misses       4001     3997       -4

Flag	Coverage Δ
#multiple	90.68% <100%> (ø)	⬆️
#single	42.98% <61.53%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
pandas/tseries/offsets.py	96.95% <ø> (+0.11%)	⬆️
pandas/core/resample.py	96.76% <100%> (+0.18%)	⬆️
pandas/core/arrays/datetimes.py	98.24% <100%> (ø)	⬆️
pandas/util/testing.py	87.58% <0%> (+0.09%)	⬆️

---

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[codecov]

Codecov Report

Merging #24330 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #24330      +/-   ##
==========================================
+ Coverage   92.28%   92.28%   +<.01%     
==========================================
  Files         162      162              
  Lines       51831    51817      -14     
==========================================
- Hits        47830    47819      -11     
+ Misses       4001     3998       -3

Flag	Coverage Δ
#multiple	90.69% <100%> (ø)	⬆️
#single	42.99% <61.53%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
pandas/tseries/offsets.py	96.95% <ø> (+0.11%)	⬆️
pandas/core/resample.py	96.76% <100%> (+0.18%)	⬆️
pandas/core/arrays/datetimes.py	98.24% <100%> (ø)	⬆️
pandas/core/indexes/period.py	93.09% <0%> (+0.03%)	⬆️
pandas/core/reshape/tile.py	94.82% <0%> (+0.06%)	⬆️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[jreback]

thanks @mroeschke