tests/bsim bt host/security/*: Test scripts cleanup

Use the common scripts to perform common functions
and do a cleanup.
Do not set variables to their defaults, set things
closer to were they are needed;
Do not perform unnecesary checks;
And in general avoid unnecessary complexity.

Some of the _compile scripts were rotten => Fix them.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>