Taxonomy: Improve backward compatibility on the wp-admin/term.php page.

Specifically, run `do_action( 'edit-tags.php' );` on this new term edit page introduced in [36308]. Changes the GET param back to `tag_ID` and properly sets the screen base in `WP_Screen`.

See #34988.

git-svn-id: https://develop.svn.wordpress.org/trunk@36874 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/admin-bar.php

@@ -573,7 +573,7 @@ function wp_admin_bar_edit_menu( $wp_admin_bar ) {
 					'href' => get_permalink( $post->ID )
 				) );
 			}
-		} elseif ( 'edit-tags' == $current_screen->base
+		} elseif ( 'term' == $current_screen->base
 			&& isset( $tag ) && is_object( $tag ) && ! is_wp_error( $tag )
 			&& ( $tax = get_taxonomy( $tag->taxonomy ) )
 			&& $tax->public )