VSE: Add sample tool

This tool is set as default tool, so default action on click doesn't have pernament effect.

Reviewed By: campbellbarton

Differential Revision: D7064

source/blender/windowmanager/intern/wm_toolsystem.c

@@ -707,7 +707,7 @@ static const char *toolsystem_default_tool(const bToolKey *tkey)
         case SEQ_VIEW_SEQUENCE:
           return "builtin.select";
         case SEQ_VIEW_PREVIEW:
-          return "builtin.annotate";
+          return "builtin.sample";
         case SEQ_VIEW_SEQUENCE_PREVIEW:
           return "builtin.select";
       }