Pre-compute values to speed up first search

[Hexicube]

On my system (i5 8600k) I get the following times for 5 runs using test data 15/7/13/30:
Old: 5.74s 5.41s 4.89s 5.04s 5.03s
New: 5.04s 4.73s 4.00s 3.97s 3.99s
Fastest times after 2 runs is likely due to JIT compilation, I did not restart the cracker between runs.

This is likely far more pronounced on slower systems.

Contains two changes:

1. Added explicit next8 and next8and16 functions to SimpleRandom, which skips having to check if the input is a power of 2.
2. Acceptable values for the results of randomness are worked out before the core loop, changing the entire logic to just 3 lookups.

[Hexicube]

Changes made.

[HyperCodec]

Changes made.

you didn't mark it as changed lol