REF: Skip transformations if 'noop' & deprecate 'skip_equivalent'

[snowman2]

• Tests added
• Fully documented, including history.rst for all changes and api/*.rst for new API

Skip equivalent/exact same is not needed. This means that one less CRS object is needed when re-creating _Transformer across threads.

>>> from pyproj import CRS, Transformer
>>> crs = CRS(4326)
>>> tr = Transformer.from_crs(crs.to_proj4(), "+init=epsg:4326")
>>> tr.name
'noop'
>>> CRS(crs.to_proj4()) == "+init=epsg:4326"
True
>>> CRS(crs.to_proj4()).is_exact_same("+init=epsg:4326")
False

[codecov]

Codecov Report

Merging #824 (5a8a13f) into master (9818912) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #824   +/-   ##
=======================================
  Coverage   95.15%   95.16%           
=======================================
  Files          21       21           
  Lines        1652     1655    +3     
=======================================
+ Hits         1572     1575    +3     
  Misses         80       80           

Impacted Files	Coverage Δ
pyproj/transformer.py	95.93% <100.00%> (+0.06%)	⬆️

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