Asset Browser: Enable by default in alpha builds

The Asset Browser is still considered an experimental feature right now. But it
can be enabled by default for alpha builds, to get further testing and
feedback. It will hopefully be a non-experimental feature by the end of bcon1.
This is done in agreement with Dalai.

source/blender/blenkernel/BKE_blender_version.h

@@ -39,7 +39,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 1
+#define BLENDER_FILE_SUBVERSION 2
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file

source/blender/blenkernel/intern/blendfile.c

@@ -647,6 +647,10 @@ UserDef *BKE_blendfile_userdef_from_defaults(void)
   BKE_studiolight_default(userdef->light_param, userdef->light_ambient);
 
   BKE_preferences_asset_library_default_add(userdef);
+  /* Enable asset browser features by default for alpha testing.
+   * BLO_sanitize_experimental_features_userpref_blend() will disable it again for non-alpha
+   * builds. */
+  userdef->experimental.use_asset_browser = true;
 
   return userdef;
 }

source/blender/blenloader/intern/versioning_userdef.c

@@ -826,6 +826,13 @@ void blo_do_versions_userdef(UserDef *userdef)
     }
   }
 
+  if (!USER_VERSION_ATLEAST(293, 2)) {
+    /* Enable asset browser features by default for alpha testing.
+     * BLO_sanitize_experimental_features_userpref_blend() will disable it again for non-alpha
+     * builds. */
+    userdef->experimental.use_asset_browser = true;
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *