Rework permissions for Security Configuration page

Problematics

For checking permissions for Security Configuration page we're using the SecurityDashboardsPermissions module.

It's handy, but has some limitations:

1. The Configuration page is independent of the Security Dashboard feature. This page is also related to the License List page which has separate permission levels from the Security dashboard, as well as the Dependency List page.
2. In the future, if some of the features will go to Core, we can have problems dividing permissions for different features
3. With adding the POST action to set auto_fix setting (permissions Maintainer+), SecurityDashboardsPermissions module doesn't cover this scenario and can be applied only to show action.

Suggested implementation plan:

1. Create a policy for read_security_configuration with permission level Developer+
2. Use this policy in Projects::Security::ConfigurationController for show action.
3. Remove usage of SecurityDashboardsPermissions from the same controller.