Combat improvements

[hjk22]

Changes:

• Added the check for the received ammo supplies event.
• Updated unable_handler to handle other targets beside boss. Now used also for mystery nodes when FocusOnMysteryNodes is enabled.
• Threads used for the checks done by movement_handler are more specific and targeted to the map currently farmed, i.e. only threads strictly necessary to the current map are prepared.
• New ClearingMode option for story maps, which simply disables the checks for ambushes (fleetlock is still not supported).
• Optimized get_fleet_location method. Fleet location is now calculated only when necessary to do so and it's mainly tracked by movement_handler instead.

[hjk22]

Update:

• Fixed retirement's filters logic in case it's the only module enabled which clears the dock.
• Other minor corrections.