LibOverride Auto Resync: Add option to disable it in Experimental userpref.

Some older .blend files won't react nicely to auto-resync, they need to
get manually fixed with `resync enforce` first.

release/scripts/startup/bl_ui/space_userpref.py

@@ -2269,6 +2269,7 @@ class USERPREF_PT_experimental_debugging(ExperimentalPanel, Panel):
         self._draw_items(
             context, (
                 ({"property": "use_undo_legacy"}, "T60695"),
+                ({"property": "override_auto_resync"}, "T83811"),
                 ({"property": "use_cycles_debug"}, None),
             ),
         )

source/blender/blenkernel/intern/blendfile.c

@@ -395,7 +395,7 @@ static void setup_app_data(bContext *C,
     BKE_main_id_refcount_recompute(bmain, false);
   }
 
-  if (mode != LOAD_UNDO) {
+  if (mode != LOAD_UNDO && !USER_EXPERIMENTAL_TEST(&U, no_override_auto_resync)) {
     BKE_lib_override_library_main_resync(
         bmain,
         curscene,

source/blender/makesdna/DNA_userdef_types.h

@@ -635,6 +635,7 @@ typedef struct UserDef_FileSpaceData {
 typedef struct UserDef_Experimental {
   /* Debug options, always available. */
   char use_undo_legacy;
+  char no_override_auto_resync;
   char use_cycles_debug;
   char SANITIZE_AFTER_HERE;
   /* The following options are automatically sanitized (set to 0)
@@ -645,7 +646,7 @@ typedef struct UserDef_Experimental {
   char use_switch_object_operator;
   char use_sculpt_tools_tilt;
   char use_asset_browser;
-  char _pad[7];
+  char _pad[6];
   /** `makesdna` does not allow empty structs. */
 } UserDef_Experimental;
 

source/blender/makesrna/intern/rna_userdef.c

@@ -6245,6 +6245,14 @@ static void rna_def_userdef_experimental(BlenderRNA *brna)
       "Undo Legacy",
       "Use legacy undo (slower than the new default one, but may be more stable in some cases)");
 
+  prop = RNA_def_property(srna, "override_auto_resync", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_negative_sdna(prop, NULL, "no_override_auto_resync", 1);
+  RNA_def_property_ui_text(
+      prop,
+      "Override Auto Resync",
+      "Enable library overrides automatic resync detection and process on file load. Disable when "
+      "dealing with older .blend files that need manual Resync (Enforce) handling");
+
   prop = RNA_def_property(srna, "use_new_point_cloud_type", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "use_new_point_cloud_type", 1);
   RNA_def_property_ui_text(