Allow disabling specific sides for human or AI players only

[MortonPL]

Currently the only way to restrict side selection is via co-op map settings, game mode settings or game option checkboxes. This PR expands the way modders can restrict selection (only for game modes) for human players and computer players separately, using DisallowedHumanPlayerSides and DisallowedComputerPlayerSides.

Example usage in INI/MPMaps.ini:

[Standard]                          ; any game mode section
; (...)
DisallowedPlayerSides=7             ; already exists - disallow sides for all players
DisallowedHumanPlayerSides=1,2,3    ; new - disallow sides for human players only
DisallowedComputerPlayerSides=4,5,6 ; new - disallow sides for computer players only

[github-actions]

Nightly build for this pull request:

• artifacts-YR.zip
• artifacts-Ares.zip
• artifacts-TS.zip
  This comment is automatic and is meant to allow guests to get latest automatic builds without registering. It is updated on every successful build.

[MortonPL]

Upon further testing, it seems that players joining a multiplayer room still don't respect the new restrictions. This will be addressed in a few days.

[MortonPL]

This should be ready for review again.

[mbnq]

Works great in BF.