API: expose dtypes in pandas.api.types

[jreback]

xref #16015
xref apache/arrow#585
xref #16042
xref #15541 (comment)

[jreback]

this is what was discussed in #16015, exposing the extension dtype constructs in pandas.api.types. This will facilitate others having permanent public location to access.

[jreback]

cc @wesm @jorisvandenbossche @TomAugspurger

I think this should fix the public exposure.

[codecov]

Codecov Report

Merging #16099 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #16099      +/-   ##
==========================================
+ Coverage   90.83%   90.84%   +<.01%     
==========================================
  Files         159      159              
  Lines       50783    50784       +1     
==========================================
+ Hits        46131    46136       +5     
+ Misses       4652     4648       -4

Flag	Coverage Δ
#multiple	88.62% <100%> (ø)	⬆️
#single	40.35% <100%> (+0.01%)	⬆️

Impacted Files	Coverage Δ
pandas/api/types/__init__.py	100% <100%> (ø)	⬆️
pandas/core/common.py	90.68% <0%> (-0.35%)	⬇️
pandas/_version.py	44.65% <0%> (+1.9%)	⬆️

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[codecov]

Codecov Report

Merging #16099 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #16099      +/-   ##
==========================================
- Coverage   90.86%   90.86%   -0.01%     
==========================================
  Files         159      159              
  Lines       50773    50771       -2     
==========================================
- Hits        46136    46133       -3     
- Misses       4637     4638       +1

Flag	Coverage Δ
#multiple	88.64% <100%> (-0.01%)	⬇️
#single	40.34% <100%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/api/types/__init__.py	100% <100%> (ø)	⬆️
pandas/core/common.py	90.68% <0%> (-0.35%)	⬇️
pandas/util/testing.py	79.13% <0%> (-0.06%)	⬇️

---

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