Use `//@ts-expect-error` to simplify testing approach

[Kostis Maninakis]

• Use //@ts-expect-error inside *.fail.test files to mark "rejected" test cases and simplify (delete altogether?) unit testing shell script.
• Consider renaming all tests to just *.test if the extra context on the filename is obsolete
• Keep current behavior where our test runner continues testing subsequent suits after a failing suit and prints out each one that failed