[CLN] cleanup import reverse-dependencies

[jbrockmendel]

Parts of the code are made more difficult to reason about by depending on pandas.io.formats, which has dependencies all over the code.

This PR starts in on this by replacing import Foo with import ABCFoo where possible. Along the way it cleans up import order.

[WillAyd]

Think this will have any impact on the overall import time? @TomAugspurger do you know where that original issue was?

[codecov]

Codecov Report

Merging #21844 into master will decrease coverage by <.01%.
The diff coverage is 97.91%.

@@            Coverage Diff             @@
##           master   #21844      +/-   ##
==========================================
- Coverage   91.92%   91.92%   -0.01%     
==========================================
  Files         160      160              
  Lines       49916    49906      -10     
==========================================
- Hits        45885    45875      -10     
  Misses       4031     4031

Flag	Coverage Δ
#multiple	90.3% <97.91%> (-0.01%)	⬇️
#single	42.11% <44.79%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
pandas/plotting/_converter.py	63.2% <100%> (ø)	⬆️
pandas/plotting/_timeseries.py	64.94% <100%> (-0.36%)	⬇️
pandas/io/clipboards.py	100% <100%> (ø)	⬆️
pandas/io/formats/csvs.py	97.66% <100%> (-0.02%)	⬇️
pandas/plotting/_tools.py	72.62% <100%> (-0.31%)	⬇️
pandas/io/formats/format.py	98.24% <100%> (-0.01%)	⬇️
pandas/io/formats/excel.py	97.37% <100%> (ø)	⬆️
pandas/io/pytables.py	92.48% <100%> (ø)	⬆️
pandas/io/formats/html.py	88.85% <100%> (ø)	⬆️
pandas/io/sas/sas_xport.py	90.27% <100%> (ø)	⬆️
... and 3 more

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[jreback]

thanks @jbrockmendel

yeah this is almost cosmetic as python optimizes the imports, but it is nicer if can consolidate the imports at the top and avoid importing-chain deps.

if you can contrive a linter to actually conform the import orderings (e.g. _libs, util, compat, core), would be great, but might be tricky.