UI: support searching for more recent files

When trying to find and open an older file, it is annoying when it is not in the
recent files list anymore. This patch increases the length of the recent files
list, without making the menu huge by making better use of menu-search.

Specifically the following is changed: * Number of remembered recent files is
increased from 20 to 200 by default. * The recent files menu is limited to 20
entries. * When activating menu search (by pressing space when in the menu), all
available recent files can be searched. * There is a new "More..." menu entry at
the bottom, which also activates the menu search.

Pull Request: https://projects.blender.org/blender/blender/pulls/146884

release/datafiles/userdef/userdef_default.c

@@ -140,7 +140,7 @@ const UserDef U_default = {
     .pad_rot_angle = 15,
     .rvisize = 25,
     .rvibright = 8,
-    .recent_files = 20,
+    .recent_files = 200,
     .smooth_viewtx = 200,
     .glreslimit = 0,
     .color_picker_type = USER_CP_CIRCLE_HSV,