👼 Script: Log meaningful error upon callback mixup.

[ohlidalp]

One point for @Xploder98 in a friendly Devs vs. Users match :)

Long story short, Xploder mixed up callbacks and the game obligued which resulted in script failure with error asCONTEXT_NOT_PREPARED. This hapenned because our callback system is very confusing:

• we have a legacy "script handler" mechanic in .TOBJ file and classic game.spawnObject(), where you pass a function name and it gets invoked on eventbox collision.
• we also have recently introduced SE_EVENTBOX_ENTER and SE_EVENTBOX_EXIT which work with the classic event callback mechanism eventCallback() (and the extended eventCallbackEx() version) - it does the same job and even provides some extra data. This works independently of the "script handler" mecahnic described above - you just do game.registerForEvent(SE_EVENTBOX_ENTER) and you're covered, for all objects.

Changes made:

• clarified the legacy eventbox callback in docs on 'developer.rigsofrods.org' (will update when this commit/PR is merged).
• Added a "this is obsolete" notice to AngelScript.log, see below.
• Added a sensible "did you make a typo in arguments?" notice to AngelScript.log, see below.

Example AngelScript.log if you mix up the callbacks:

13:03:15: spawnObject(): Specifying event handler function in `game.spawnObject()` is obsolete and only works with terrain scripts; Use `eventCallbackEx()` with event `SE_EVENTBOX_ENTER` instead, it provides the same data and works with any script. Just pass an empty string to the `game.spawnObject()` parameter.
13:03:15: Warning: a callback function with signature 'void eventCallback(int, string, string, int)' was not found but a function with given name exists: 'void eventCallback(int, int)' - did you make a typo in arguments?

What needs to be tested:

• Terrain scripts should work normally: check races, spawners and truckshops.
• Custom scripts like 'demo_script.as' or 'road_editor.as' should work normally.

[CuriousMike56]

Tested:
Truckshops ✅
Races ✅
Demo script ✅
Road editor ✅
Script editor ✅

Only new warning I've seen is on the "GPU benchmark" terrain (Benchmark.zip) where every tree spawned shows:
[RoR|Script|Notice] Warning: a callback function with signature 'void e(int, string, string, int)' was not found
The script still works as normal.