chore(extensions): clean up backend entrypoints and file globs (#38360)

superset-extensions-cli/src/superset_extensions_cli/templates/backend/pyproject.toml.j2

@@ -2,3 +2,10 @@
 name = "{{ backend_package }}"
 version = "{{ version }}"
 license = "{{ license }}"
+
+[tool.apache_superset_extensions.build]
+# Files to include in the extension build/bundle
+include = [
+    "src/{{ backend_path|replace('.', '/') }}/**/*.py",
+]
+exclude = []

superset-extensions-cli/src/superset_extensions_cli/templates/extension.json.j2

@@ -4,11 +4,5 @@
   "displayName": "{{ display_name }}",
   "version": "{{ version }}",
   "license": "{{ license }}",
-  {% if include_backend -%}
-  "backend": {
-    "entryPoints": ["{{ backend_entry }}"],
-    "files": ["backend/src/{{ backend_path|replace('.', '/') }}/**/*.py"]
-  },
-  {% endif -%}
   "permissions": []
 }