LPS-40223 Centralize gathering of roles of teams of a certain group to the service layer

Hi Ray,

I made the modifications Brian asked for (changing the return type from Collection<E> to List<E>): https://github.com/brianchandotcom/liferay-portal/pull/14025#issuecomment-24897305

Nevertheless, I think he was right regarding method getGroupRoles_1to4(), it belongs to an unused call chain and thus unreachable, but getGroupRoles_5() is being used actively only its naming is unfortunate. I removed dead code and did a rename.

PermissionExportImportTest passes, so I think this part is going to be right, though take a thorough look through the code please.

Thx,
László

/CC:@zsigmondrab