[Grace] Adds complete testing suite

[apostolis1]

This PR adds the complete testing suite we created during the development of our compiler

The tests are placed in a separate directory as to not intervene with existing open PRs that are also adding tests to the directory /grace/programs

[kostis]

Thanks for your PR - it's very good! (However, please fix the failing tests; you can use answer for ans.)

[apostolis1]

Fixed typos and errors reported by codespell and shellcheck