Fix #30958: Right click menu and add shortcut for importers/exporters doesn't work

This was caused by how keymap is guessing for importer/exporter:

- In some cases if detected wrong keymap like for IMPORT_CURVE_OT_svg
  curve editing context was used because of CURVE_OT substring in
  operator name
- In other cases no keymap was detected because of substrings
  WM_keymap_guess_opname cheched.

Fixed by using Window keymap for any operator with EXPORT_/IMPORT_ substring
which seems to detect importer/exporter operator and only them nicely.

source/blender/windowmanager/intern/wm_keymap.c

@@ -1190,6 +1190,10 @@ wmKeyMap *WM_keymap_guess_opname(const bContext *C, const char *opname)
 	else if (strstr(opname, "MARKER_OT")) {
 		km = WM_keymap_find_all(C, "Markers", 0, 0);
 	}
+	/* Import/Export*/
+	else if (strstr(opname, "IMPORT_") || strstr(opname, "EXPORT_")) {
+		km = WM_keymap_find_all(C, "Window", 0, 0);
+	}
 	
 	
 	/* 3D View */