Perform packing/unpacking of arguments and results in HDL

[martijnbastiaan]

Running three experiments with the old and the new code shows that avoiding packing/unpacking in Haskell yields a ~50% performance increase for longer running tests.

Figures are taken by observing clash-vexriscv-sim:unittests's debug times.

Old 1	Old 2	Old 3	Old min	New 1	New 2	New 3	New min	New faster
0.25	0.31	0.3	0.25	0.28	0.24	0.26	0.24	4.2%
0.65	0.69	0.74	0.65	0.51	0.48	0.5	0.48	35.4%
0.44	0.48	0.53	0.44	0.36	0.31	0.34	0.31	41.9%
1.84	1.72	1.7	1.7	1.12	1.08	1.12	1.08	57.4%
1.57	1.58	1.58	1.57	1.03	1.06	1.01	1.01	55.4%
0.43	0.4	0.4	0.4	0.33	0.33	0.32	0.32	25.0%
4.62	4.18	4.5	4.18	2.69	2.73	2.73	2.69	55.4%
0.17	0.18	0.24	0.17	0.18	0.24	0.23	0.18	-5.6%
2.26	2.57	2.43	2.26	1.35	1.45	1.42	1.35	67.4%

I'm overrunning my timebox though, so I'm putting this as "Draft".

TODO

• Include Verilog
• Test