Let LuaComponent respect bImplicitSelf

[micheljung]

My idea is to connect a Lua table to an Actor, but without "mixing" them.

So UShipLuaComponent::LuaObject references the Lua table:

/** The Lua table that is connected to this actor component. */
FLuaValue LuaObject;

When the actor is spawned, a Lua table should be created for it:

void UShipLuaComponent::BeginPlay()
{
  Super::BeginPlay();

  const TArray Args = {FLuaValue(this)};
  LuaObject = LuaCallFunction("Ship.Init", Args, true);
}

--- This function is called by the engine whenever a [Ship] actor is spawned.
---@param actor ShipActor the engine actor that is connected to this table
function Ship.Init(actor)
  local instance = setmetatable({}, Ship)
  instance.Actor = actor
  return instance
end

The reason I do this is because modders should be able to add functions to Ship:

-- HasTarget should not have to exist in the LuaComponent
function Ship:HasTarget()
  return self.Target ~= nil
end

But they can also delegate to the LuaComponent:

---@param input number Value from `0.0` - `1.0`
function Ship:SetThrottleInput(input)
  self.Actor.SetThrottleInput(input)
end

And when the engine calls a function like Tick, self should be the Lua table, not the LuaComponent:

function Ship:Tick(deltaTime)
  print("Tick "..deltaTime)
end

To achieve this, I need to be able to call a Lua function without passing the LuaComponent implicitly as self. I thought that the setting bImplicitSelf = false would achieve this. But in methods like LuaCallFunction, this flag is not respected.

This PR fixes that.

Unfortunately, this is a breaking change. To preserve the old behavior, bImplicitSelf would need to default to true, but that would also be a breaking change.

Maybe I'm not getting it right anyway. In that case, maybe a new flag could be introduced to control the behavior? Then it would also not be breaking.

[micheljung]

How about this as a (transitional?) opt-in solution:

  /**
   * Whether to implicitly pass this component as the first argument (usually <code>self</code> when calling a Lua
   * function.
   *
   * Currently, this is only respected by <code>ULuaState::MetaTableFunction__call</code> and
   * <code>ULuaState::MetaTableFunction__rawcall</code>. If you want this to work for <code>LuaCall...</code> functions
   * as well, you need to enable <code>bImplicitSelfForLuaCalls</code>, too.
   */
  UPROPERTY(EditAnywhere, Category = "Lua")
  bool bImplicitSelf;

  /**
   * When enabled, <code>bImplicitSelf</code> will be respected by all <code>LuaCall...</code> functions.
   *
   * See <a href="https://github.com/rdeioris/LuaMachine/pull/77">this PR</a>.
   */
  UPROPERTY(EditAnywhere, Category = "Lua")
  bool bImplicitSelfForLuaCalls;

[micheljung]

Please check that I'm not doing it wrong here; see line 108

[micheljung]

Same, see line 151