Chore: Group auth docker blocks (#54274)

* Move auth docker images to parent folder

* Add README file for auth parent folder

* Add grafana-authnz-team as code owner

* Update `devenv` docs

devenv/docker/blocks/auth/openldap-mac/docker-compose.yaml

@@ -0,0 +1,15 @@
+  openldap-mac:
+    container_name: ldap
+    image: osixia/openldap
+    environment:
+      LDAP_ORGANISATION: grafana
+      LDAP_DOMAIN: grafana.org
+      LDAP_ADMIN_PASSWORD: grafana
+      LDAP_SEED_INTERNAL_LDIF_PATH: /tmp/smt/
+    ports:
+      - 389:389
+      - 636:636
+    restart: unless-stopped
+    volumes:
+      - ./docker/blocks/openldap-mac/prepopulate/:/tmp/smt/
+      - ./docker/blocks/openldap-mac/modules/:/tmp/smt/