Port identification tests from colcon_core

[cottsay]

This doesn't exhaustively test colcon_ros.package_identification.ros, but it does give us some basic coverage.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 15.53%. Comparing base (c5452db) to head (820bfed).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #157      +/-   ##
==========================================
+ Coverage    6.92%   15.53%   +8.61%     
==========================================
  Files          20       20              
  Lines         650      650              
  Branches      139      139              
==========================================
+ Hits           45      101      +56     
+ Misses        605      539      -66     
- Partials        0       10      +10     

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[nuclearsandwich]

I know this is adapted directly from colcon core. A drive-by review comment is that these looong test functions are something of an anti-pattern because the test stops at the first assert which means it may take a few iterations to pass again after failing. But having said my piece, imperfect tests are infinitely preferred to no tests.