chore: create type for unique role names (#13506)

* chore: create type for unique role names

Using `string` was confusing when something should be combined with
org context, and when not to. Naming this new name, "RoleIdentifier"

coderd/members.go

@@ -68,7 +68,7 @@ func convertOrganizationMember(mem database.OrganizationMember) codersdk.Organiz
 	}
 
 	for _, roleName := range mem.Roles {
-		rbacRole, _ := rbac.RoleByName(rbac.RoleName(roleName, mem.OrganizationID.String()))
+		rbacRole, _ := rbac.RoleByName(rbac.RoleIdentifier{Name: roleName, OrganizationID: mem.OrganizationID})
 		convertedMember.Roles = append(convertedMember.Roles, db2sdk.SlimRole(rbacRole))
 	}
 	return convertedMember