tools: implement an -s option for v ast, to skip all nodes with default values like [], {}, 0, false; with it v ast -pts examples/hello_world.v | wc -l is 36 lines

tools: implement an -s option for v ast, to skip all nodes with default values like [], {}, 0, false; with it v ast -pts examples/hello_world.v | wc -l is 36 lines #13800