Added a single test function script and fix debug-test.sh to be more robust (#7279)

* run-single-test.sh: added a single test function script and fix debug-test.sh to be more robust

* debug-test.sh: combined execute and gdb test mode via -g flag

* debug-test.sh: refactor

* debug-test: refactor for clarity

* debug-test.sh: comment style changes

* debug-test.sh: fix gdb