MDL-69231 behat: remaining work for role capability generator

This commit does few things:
* Unify data generators usage to role short name.
* Replace remaining manual steps to use the new data generator.
* Also replaced other manual steps to set config to use data generators.
* Tidy up of some tests, aligning pipes and splitting one line steps into multiple lines.
* Fixes tests to have one Given/When/Then per scenario.

lib/testing/generator/data_generator.php

@@ -871,9 +871,9 @@ EOD;
     /**
      * Set role capabilities for the specified role.
      *
-     * @param   int $roleid The Role to set capabilities for
-     * @param   array $rolecapabilities The list of capability =>permission to set for this role
-     * @param   context $context The context to apply this capability to
+     * @param int $roleid The Role to set capabilities for
+     * @param array $rolecapabilities The list of capability =>permission to set for this role
+     * @param null|context $context The context to apply this capability to
      */
     public function create_role_capability(int $roleid, array $rolecapabilities, context $context = null): void {
         // Map the capabilities into human-readable names.