tests bsim_bt: Add scripts to compile and run tests

The compile.sh script compiles the neccessary applications to run
all testcases.

The run_parallel.sh script runs all avaliable tests scripts
(e.g.
tests/bluetoothbsim_bt/bsim_test_app/tests_scripts/Basic_con.sh )
and reports which of them pass or fail.

Note that the run_parallel script will run the test in parallel
only if it can find GNU parallel (which is missing in CI),
otherwise it just runs them in serial

Signed-off-by: Alberto Escolar Piedras <alpi@oticon.com>