自己写的一个移位寄存器的实例，该例子主要用来讲述verilog中的testbench的写作，以及在testbench中怎样使用task，以使仿真更加的高效简洁-Write your own instance of a shift register, which is mainly used to describe examples of verilog testbench writing, as well as how to use the testbench in the task, to m