Fix accumulated issues with campaigns

[IvanSavenko]

Progress so far:

• extract campaign-related code from CGameState
• reorganize CampaignHandler / CampaignState code
• rewrite heroes crossover code to match H3 logic
• fix transfer of artifacts kept by heroes
• check that game picks strongest heroes (and not weakest) for transfer
• check that game places heroes by power in same order as in H3
• recheck removal of reserved heroes

Campaigns that should be tested to confirm functionality of most of edge cases:

• Spoils of War (player selectable heroes, and even - color to play in 3rd scenario)
• Armageddon Blade (a lot of hero & artifact transfer shenanigans)
• Unholy Alliance (a lot of hero & artifact transfer shenanigans)

Issues to confirm and fix:

• Error with custom campaign #1902
• In Rise of the Necromancer campaign, Sandro can not bring cloak of the undead Lord to next scenario #2204
• Campaign hero starts without quest artifacts #2134
• Game crashes on campaign advance with mods #2103
• Bonus mage guild in RoE Seeds of Discontent campaign second scenario is not working properly #2049
• Authenticity campaign bugs with the original #1167
• Unholy Alliance, scenario Final Peace - Gem and Clancy have correct skill, but have 1st level. Should be on the 25th.
• Dragon Slayer, first scenario - Dracon should start without spellbook (h3m parsing issue?) (https://bugs.vcmi.eu/view.php?id=3104)
• Campaign UI - all campaigns are (unnamed)
• Campaign UI - map name won't update on changing selected scenario
  (https://bugs.vcmi.eu/view.php?id=1695)
• Campaign UI - custom music track is not playing

Postponed (to be moved to separate issue)

• Asylum (user-made campaign) - Hero placeholder (by type) should be replaced even hero was not owned before
• Dungeons and Devils, scenario A Devilish Plan - defeating quest monster leads to game over (https://bugs.vcmi.eu/view.php?id=2170)
• Birth of Barbarian - has "if you lose either component of the Angelic Alliance, the scenario is lost" as additional loss condition
• New Beginning, Unholy Alliance - Gem has her class set to "Sorceress"

[dydzio0614]

while you are at it, dragon slayer campaign should be tested for creatures carryover from 1st mission

[IvanSavenko]

@dydzio0614
Fixed discovered regression with creatures transfer like 5-10 minutes ago. Can confirm that it works on this branch

[IvanSavenko]

Presumably complete.

Few campaigns still have few minor issues to solve, but those are not trivial to fix, will move them to separate issues after merge