AI should determine best skill when leveling up heroes

[idshibanov]

Currently AI just rolls randomly when picking a new secondary skills. This decision should be driven by a value estimation, same as everything else.

[ihhub]

Hi @idshibanov , please rebase your branch from master to fix GitHub Actions.

[crypt47]

Hello, I've always wanted to ask if Mysticism has any value. It looks like it has pretty many scores in descision making code, but it only gives you something like 4 sp/day at max. This is pretty low, especially for magic heroes who may use 100 sp and more during one battle. If it was me, I've either raised the sp/day ratio, or lowered this skill stratigic value. It's much more interesting to have more competitive skills then junk skills. Also the number of well objects matters.

[oleg-derevenetz]

Hi @idshibanov I rebased this PR against master to resolve conflicts after #8986, could you please take a look, just in case?

[ihhub]

@idshibanov , thank you so much for this improvement!