[WIP] Remove all ROS infrastructure and run tests via Tox

[emersonknapp]

This PR makes cross_compile into a plain-python package, removing the ROS infrastructure around it.

It uses tox to run tests in place of colcon test, depending on the ament linters via a pip VCS URL.

Fixes #109 Fixes #111

[codecov[bot]]

Codecov Report

Merging #121 into emersonknapp/python-ci will decrease coverage by 10.44%. The diff coverage is 16.66%.

@@                     Coverage Diff                     @@
##           emersonknapp/python-ci     #121       +/-   ##
===========================================================
- Coverage                   87.36%   76.92%   -10.45%     
===========================================================
  Files                           6        3        -3     
  Lines                         372      221      -151     
===========================================================
- Hits                          325      170      -155     
- Misses                         47       51        +4

Flag	Coverage Δ
#unittests	76.92% <16.66%> (-10.45%)	:arrow_down:

Impacted Files	Coverage Δ
cross_compile/ros_cross_compile.py	69.23% <ø> (ø)
cross_compile/__main__.py	0% <0%> (ø)
cross_compile/sysroot_compiler.py	80.79% <100%> (-0.22%)	:arrow_down:
test/test_colcon_mixins.py
cross_compile/__init__.py
test/test_sysroot_compiler.py

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[emersonknapp]

Closing in favor of https://github.com/ros-tooling/cross_compile/pull/123