For the case where there are code changes outside of the
implementation directories, sort the implementations that have actual
changes in their own directory to the top of the matrix.
- Dynamically generate a strategy matrix based on the list of changed
files in this push/pull_request. If the changed files are restricted
to implementations then only generate a matrix with those
implementations. If the changes are to tests or other
non-documentation files (runtest.py, IMPLS.yml, .github/*, etc) then
run the full set. The matrix generation is done in get-ci-matrix.py.
- Split the implementation list for Github Actions out into a separate
yaml file IMPLS.yml
- Reduce the travis file to just the OS X / XCode related builds that
aren't supported on Github Actions.
- Rename the .travis_test.sh script to ci.sh since it is the general
CI script used for both Travis CI and Github Actions.
