Make layout support compatible with enhanced pagination (#55416)

* Make layout supports compatible with enhanced pagination

* Use sanitize_title and add `layout` to the class name

lib/block-supports/layout.php

@@ -527,6 +527,26 @@ function gutenberg_get_layout_style( $selector, $layout, $has_block_gap_support
 	return '';
 }
 
+/**
+ * Generates an incremental ID that is independent per each different prefix.
+ *
+ * It is similar to `wp_unique_id`, but each prefix has it's own internal ID
+ * counter to make each prefix independent from each other. The ID starts at 1
+ * and increments on each call. The returned value is not universally unique,
+ * but it is unique across the life of the PHP process and it's stable per
+ * prefix.
+ *
+ * @param  string $prefix Prefix for the returned ID.
+ * @return string         Incremental ID per prefix.
+ */
+function gutenberg_incremental_id_per_prefix( $prefix = '' ) {
+	static $id_counters = array();
+	if ( ! array_key_exists( $prefix, $id_counters ) ) {
+			$id_counters[ $prefix ] = 0;
+	}
+	return $prefix . (string) ++$id_counters[ $prefix ];
+}
+
 /**
  * Renders the layout config to the block wrapper.
  *
@@ -608,7 +628,16 @@ function gutenberg_render_layout_support_flag( $block_content, $block ) {
 
 	$class_names        = array();
 	$layout_definitions = gutenberg_get_layout_definitions();
-	$container_class    = wp_unique_id( 'wp-container-' );
+
+	/*
+	* We use an incremental ID that is independent per prefix to make sure that
+	* rendering different numbers of blocks doesn't affect the IDs of other
+	* blocks. We need this to make the CSS class names stable across paginations
+	* for features like the enhanced pagination of the Query block.
+	*/
+	$container_class = gutenberg_incremental_id_per_prefix(
+		'wp-container-' . sanitize_title( $block['blockName'] ) . '-layout-'
+	);
 
 	// Set the correct layout type for blocks using legacy content width.
 	if ( isset( $used_layout['inherit'] ) && $used_layout['inherit'] || isset( $used_layout['contentSize'] ) && $used_layout['contentSize'] ) {