[vdmkenny]

The player's ship now lands only on a ship that offers a landing. The game's types keep the game's rules: the Reliant and the Yamato offer theirs, and no other type offers one, so the original campaign lands as before.

• ShipTypeRecord.landing holds the landing a type offers: reliant, yamato, bay, badanov, or nil for none. Load scripts change it, and a mod's [ShipType] section gives it with Landing=. Without the key, a mod's type takes its base's landing where it keeps its base's model, and none otherwise. Where a carrier's model lacks what its landing needs, such as the Reliant's launch tube or a bay's launch points, nothing lands on it and the log says so.
• A mission's script can open or close a landing on one ship (object.landing), and choose the ship PERMISSION TO LAND asks (world.player_carrier, world.set_player_carrier).
• Every Land order follows the rule: PERMISSION TO LAND's, a mission's SetAI and the friendly fire's sending home.
• A permission_to_land hook, so that a mod can answer PERMISSION TO LAND its own way.
• A landing in the Badanov's and the Krasny's bay. It shares the hangar bay's landing and comes to rest where the Badanov's launch sets a ship (launch.badanov.gatePlace).
• The landings move into ailand/reliant.zig, ailand/yamato.zig and ailand/bay.zig, as the launches are under launch/, and share their common steps in ailand.zig.

There is no --original switch: this changes how the game plays, not how it looks.

A change from #1192: a hangar bay carrier such as the Victorious, and a mod's carrier with a model of its own, no longer take the player's ship by default. A mod's carrier needs Landing=bay, or a script gives it the landing.

Checked: the tests, make check-missions, and a tick-by-tick hash of the game's state against main in missions 1, 2, 18, 20 and 30, each through a full landing (PERMISSION TO LAND pressed once the launch is over). Tried in the game with a local mod whose missions launch the player from the Badanov and the Victorious and land there.

Left:

• Any carrier other than a Yamato answers PERMISSION TO LAND with the Reliant's bridge officer (A carrier's type names the bridge officer who answers PERMISSION TO LAND #1340).
• make ghidra-annotate didn't run, since a Ghidra window holds the project. The landing's exported types change: LandStyle gains badanov and loses none, and LandState.style becomes a number.

BEGIN_COMMIT_OVERRIDE
feat: mods and missions choose which ships the player can land on (#758)
feat: the player's ship can land in the Badanov's and the Krasny's bay
feat: scripts can hook PERMISSION TO LAND and choose the player's carrier
END_COMMIT_OVERRIDE

Closes #758