Port environment hook tests from colcon_core

[cottsay]

Requires #147

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 31.00%. Comparing base (8a69a89) to head (0c6c6ea).
Report is 1 commits behind head on cottsay/cmake-module-path-fix.

Additional details and impacted files

@@                        Coverage Diff                        @@
##           cottsay/cmake-module-path-fix     #148      +/-   ##
=================================================================
+ Coverage                          29.39%   31.00%   +1.61%     
=================================================================
  Files                                 10       10              
  Lines                                745      745              
  Branches                             165      166       +1     
=================================================================
+ Hits                                 219      231      +12     
+ Misses                               484      475       -9     
+ Partials                              42       39       -3     

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[nuclearsandwich]

Reviewing and approving based on prior approval of the needed PR.