Profile for new suites / tests

Right now, BugBug has a default profile that can't be changed (because other profiles inherit values from it).

This could be annoying if you create a new test and want to run it on a different profile - new tests/suites have a default profile set, so you have to change it every time a new test is created.

To fix it, we want to add an option to change this behavior for new tests/suites.

Existing behavior will not change - the default profile will remain the default.

Worth noting: if the user changes a profile for a single test, BugBug stores this information for it. This behavior remains.