Create a generic pulse_generator to stimulate signals. It can generate pulses on toggle, posedge, and negedge.
Add back fill_fifo testbench and do file. Make small fix to end-of-line address increment in FSM.

The testbench does this:

Each line has 128 pixels of 4 bytes. The stride is a much larger number at 0x4000. Draw 3 lines and then assert vsync (end-of-frame).