feat: roles unification (#3999)

https://linear.app/unleash/issue/2-1137/roles-unification-on-the-ui

Root and project roles should be managed in a similar manner, which
means using the same roles route and tab for both.

Additionally, this includes a big revamp to the project roles to align
them more closely with the modern and standardized custom root roles
that were recently developed. They mostly use the same components.

There are still more things we want to improve and unify, but we've left
some of that out of this PR due to PR size concerns.

frontend/src/component/admin/Admin.tsx

@@ -13,10 +13,7 @@ import { InstanceAdmin } from './instance-admin/InstanceAdmin';
 import { MaintenanceAdmin } from './maintenance';
 import AdminMenu from './menu/AdminMenu';
 import { Network } from './network/Network';
-import CreateProjectRole from './projectRoles/CreateProjectRole/CreateProjectRole';
-import EditProjectRole from './projectRoles/EditProjectRole/EditProjectRole';
 import { Roles } from './roles/Roles';
-import ProjectRoles from './projectRoles/ProjectRoles/ProjectRoles';
 import { ServiceAccounts } from './serviceAccounts/ServiceAccounts';
 import CreateUser from './users/CreateUser/CreateUser';
 import EditUser from './users/EditUser/EditUser';
@@ -28,11 +25,6 @@ export const Admin = () => (
         <AdminMenu />
         <Routes>
             <Route path="users" element={<UsersAdmin />} />
-            <Route path="project-roles/new" element={<CreateProjectRole />} />
-            <Route
-                path="project-roles/:id/edit"
-                element={<EditProjectRole />}
-            />
             <Route path="api" element={<ApiTokenPage />} />
             <Route path="api/create-token" element={<CreateApiToken />} />
             <Route path="users/:id/edit" element={<EditUser />} />
@@ -46,8 +38,7 @@ export const Admin = () => (
                 element={<EditGroupContainer />}
             />
             <Route path="groups/:groupId" element={<Group />} />
-            <Route path="roles" element={<Roles />} />
-            <Route path="project-roles" element={<ProjectRoles />} />
+            <Route path="roles/*" element={<Roles />} />
             <Route path="instance" element={<InstanceAdmin />} />
             <Route path="network/*" element={<Network />} />
             <Route path="maintenance" element={<MaintenanceAdmin />} />

frontend/src/component/admin/menu/AdminMenu.tsx

@@ -55,7 +55,7 @@ function AdminMenu() {
                         }
                     />
                 )}
-                {flags.customRootRoles && (
+                {isEnterprise() && (
                     <Tab
                         value="roles"
                         label={
@@ -65,16 +65,6 @@ function AdminMenu() {
                         }
                     />
                 )}
-                {flags.RE && (
-                    <Tab
-                        value="project-roles"
-                        label={
-                            <CenteredNavLink to="/admin/project-roles">
-                                <span>Project roles</span>
-                            </CenteredNavLink>
-                        }
-                    />
-                )}
                 <Tab
                     value="api"
                     label={