Upgrade to Godot 4.0 beta, only updating PC builds until further notice

Whew! I decided to take the plunge and upgrade the project to the Godot 4.0 beta. Results are mixed. While lots of things on the backend are cleaner, the instability of the beta means that I can't currently make browser builds. Hopefully that will be fixed before too long.

Changes happened all over the codebase, so I'm sure there are many bugs that have disappeared and many have arisen.

Gameplay changes:

• All maps had to be remade because the old ones were lost in the upgrade.
• Pilots have HASE scores that increase their stats appropriately (except for repairs and limited systems)
• Map tiles are animated! Nice flowing rivers.
• Weapons on the same mount now actually are shared on a mount; the aux weapon fires right after the first, both get destroyed if either do.
• Allied invades don't cause heat.
• Gave pilots callsigns in additions to regular names (and mech names)
• Updated AI to be smarter about what weapons to use and where to move
• Added more tutorial explanations ++ new characters that show up during it
• Added allied AI units
• Hidden unit sprites are darkened
• Need to confirm movement when it will trigger an enemy overwatch
• Gave demolisher resistance to melee damage
• Made Elite NPC template
• Gear without charges can't be destroyed
• Pathfinder better at predicting engagement for large untis
• Moves abort if the step is no longer valid

UI changes:

• Radial weapon/gear menu has a shadow vignette to help clean up the focus.
• Reorganized gear buttons; gave them lots of little icons and explanatory tooltips.
• Remappable keyboard and mouse controls!
• Added a little roll animation for attack rolls
• Added little nubbins to tooltips to point at one
• Redesigned character sheet and hooked up the actual unit stats
• Added tooltips to so many small things
• New shader effect for showing which buttons to push in tutorial
• Show stat crosshairs when choosing weapon target
• Added destroyed texture for wrecked gear
• Overcharge button says the heat cost
• Buffs show up in the status crosshair
• Changed dialogue system to a more light-weight manager that will make it easier to eventually make your own scenarios. Portraits do a little bounce and can move from one location to another