fix(script-engine): Count script timers at the legacy rate while time is frozen

[Okladnoj]

With GENERALS_ONLINE_HIGH_FPS_SERVER the logic runs at 60 Hz and script timers tick only
when HasLegacyFrameAdvanced() is true, which follows the parity of m_frame.

While a script freezes time, GameLogic::update still runs the script engine every tick but
returns before m_frame++, so the flag stays whatever the frozen frame left it at:

• an even frozen frame runs every script timer twice as fast (the briefing lines of MD_USA01
  start on top of each other);
• an odd frozen frame stops the timers altogether.

ScriptEngine::hasLegacyTimerTickPassed() keeps HasLegacyFrameAdvanced() whenever the frame
moves and counts its own legacy ticks while the frame stands still. Normal and network play
are unchanged: time is never frozen by script in a network game.