tools: helper script to generate a test coverage report

tools: helper script to generate a test coverage report

This script uses a heuristic approach to determine an approx.
test coverage of all util-linux tools. It does this by simply
looking at all the test scripts for a given tool and compares
the long options seen in them with all available ones for the
concerned tool. It also reports if a tool is either missing a
test subdirectory in tests/ts or doesn't have any test script
at all.

This script is not necessarily intended to be ran for build
tests but rather for code quality checks and to help util-linux
developers to get a better overview of their testing infrastructure
and plan accordingly for improvements.

It will potentially also help in keeping the tools stable and
detect regressions more efficiently.

Signed-off-by: Christian Goeschel Ndjomouo <cgoesc2@wgu.edu>