Revert NFS page variants, keep only title and icon additions

Roll back the NFS page component changes (BuiHeader, headerVariant,
NfsCatalogGraphPage, NfsDefaultImportPage) from catalog-graph and
catalog-import plugins. Only the title and icon metadata additions to the
new frontend system plugin definitions are retained.

For the kubernetes plugin, replace the generic RiShipLine icon with a
proper Kubernetes helm wheel SVG icon from Simple Icons.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

yarn.lock

@@ -5245,7 +5245,6 @@ __metadata:
     "@backstage/plugin-catalog-react": "workspace:^"
     "@backstage/plugin-permission-react": "workspace:^"
     "@backstage/test-utils": "workspace:^"
-    "@backstage/ui": "workspace:^"
     "@material-ui/core": "npm:^4.12.2"
     "@material-ui/icons": "npm:^4.9.1"
     "@material-ui/lab": "npm:4.0.0-alpha.61"
@@ -6078,7 +6077,6 @@ __metadata:
     "@backstage/plugin-permission-react": "workspace:^"
     "@backstage/test-utils": "workspace:^"
     "@material-ui/core": "npm:^4.12.2"
-    "@remixicon/react": "npm:^4.6.0"
     "@testing-library/dom": "npm:^10.0.0"
     "@testing-library/jest-dom": "npm:^6.0.0"
     "@testing-library/react": "npm:^16.0.0"