AB Testing controllers need an option to specify additional roles

Description

Related to MAR-1302

Problem:

When a user is not a member of one of the default roles (such as CMSAdmin or CMSEditor), the user cannot access or edit an AB Test Controllers. You can now specify a comma-separated list of one or more custom roles to provide access to the AB Test Controllers.

Solution:

1. Add a comma separated list of roles to the app keys. For example:

   <add key="EPiServer:Marketing:Testing:Roles" value="Content_Admins" />

2. Create a new mapped virtual role section. For example:

   <virtualRoles addClaims="true">

   <providers>

   ...

   <add name="LocalAdmins"

   type="EPiServer.Security.MappedRole, EPiServer.Framework"

   roles="SWE_Admins"

   mode="Any" />

   </providers>

3. Add users to those roles so they can access the UI editor again.