nir: Add a nir_metadata_all enum value

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5171>

src/compiler/nir/nir.h

@@ -2699,6 +2699,15 @@ typedef enum {
     * determine.  Most passes shouldn't preserve this metadata type.
     */
    nir_metadata_loop_analysis = 0x10,
+
+   /** All metadata
+    *
+    * This includes all nir_metadata flags except not_properly_reset.  Passes
+    * which do not change the shader in any way should call
+    *
+    *    nir_metadata_preserve(impl, nir_metadata_all);
+    */
+   nir_metadata_all = ~nir_metadata_not_properly_reset,
 } nir_metadata;
 
 typedef struct {