BUG: Fix transformer list for 3D transformations in TransformerGroup

[snowman2]

• Closes Obtaining Geoid (EGM2008) to Ellipsoid Proj Pipeline #1072
• Tests added
• Fully documented, including history.rst for all changes and api/*.rst for new API

[codecov]

Codecov Report

Merging #1075 (0d2555c) into main (f031f5f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1075   +/-   ##
=======================================
  Coverage   96.14%   96.14%           
=======================================
  Files          20       20           
  Lines        1791     1791           
=======================================
  Hits         1722     1722           
  Misses         69       69           

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