Find highest increase

[ggwpez]

paritytech/cumulus#1784 shows an example where GuessWorst shows a decrease but Base shows an increase of 426931.34%.

Introduce a new eval method where we do a linear optimization and find the highest relative increase. Should then find that.
The case where both hyper-planes have the same dimension should be easy, just subtract them and find the absolute maximum. Otherwise some more thoughts are needed.