Rename testsuites/**.doc to README.md

Summary

We have a lot of *.doc files that describe what the tests are. GitLab and every other source browser now display README.md as the default display file. Is there any reason to keep these unique named doc files around? At the very least naming them as README would follow current conventions.

Here is an example of what it would look like:

• https://gitlab.rtems.org/amar/rtems/-/tree/testsuites_readme/testsuites/

Some of the doc files are empty what should we do with those? All they contain is a license but no contents.

Is the license header necessary when the tests contain them?