LMS: refactor LMS code to avoid forcing players to join on connection

LMS: refactor LMS code to avoid forcing players to join on connection

Minor changes:

• players don't have lives in warmup stage
• players can become spectators with F3 (without forfeiting) during warmup and countdown to game start
• ready-restart moves forfeiters to spectators

Extra gameplay changes:

• LMS: players joining late get the amount of health / armor as the less healthy player with the same number of lives

It fixes #1833 (closed)

Please note that this branch needs testing in online matches as I tested it only locally with bots.