Add parsers from bin to pk and from pk to bin.

```
BenchmarkParsePk/ParsePkJson_circuit1k-4         	  595215	      1954 ns/op
BenchmarkParsePk/ParsePkBin_circuit1k-4          	       2	 522174688 ns/op
BenchmarkParsePk/ParsePkGoBin_circuit1k-4        	  623182	      1901 ns/op
BenchmarkParsePk/ParsePkJson_circuit5k-4         	       1	2861959141 ns/op
BenchmarkParsePk/ParsePkBin_circuit5k-4          	       1	2610638932 ns/op
BenchmarkParsePk/ParsePkGoBin_circuit5k-4        	  612906	      1907 ns/op
BenchmarkParsePk/ParsePkJson_circuit10k-4        	       1	5793696755 ns/op
BenchmarkParsePk/ParsePkBin_circuit10k-4         	       1	5204251056 ns/op
BenchmarkParsePk/ParsePkGoBin_circuit10k-4       	  603478	      1913 ns/op
BenchmarkParsePk/ParsePkJson_circuit20k-4        	       1	11404022165 ns/op
BenchmarkParsePk/ParsePkBin_circuit20k-4         	       1	10392012613 ns/op
BenchmarkParsePk/ParsePkGoBin_circuit20k-4       	  620488	      1921 ns/op
```

For the `10k` constraints circuit is arround `1_368_976x` improvement.
For the `20k` constraints circuit is arround `5_409_689x` improvement.