Implement functionality to set multiple cells of a TileMap with one call

[Xkonti]

Currently the only options to set a multiple tiles are:

• Call TileMap.set_cell multiple tiles
• Use a pattern

In a popular use case of procedurally generating a game map, patterns are not very useful. The only tool left is the set_cell. Both GDScript and C# when calling that function need to go through a mapping layer that then calls the internal C++ implementation. It's often that hundreds (or thousands) of cells need to be set / changed per frame. Especially in case of dynamic loading/unloading of map segments.

I believe that adding an additional functions, something like set_cells and set_area:

• set_cells - allows for passing an array (list) of same data as is currently required by set_cell. This allows for sending a set of potentially not adjacent cells:

  var cellData = new CellData[]
  {
      new CellData { layer = 0, pos = tile1_pos, atlas = 0, atlasPos = tile1_atlasPos },
      new CellData { layer = 0, pos = tile2_pos, atlas = 0, atlasPos = tile2_atlasPos },
      new CellData { layer = 0, pos = tile3_pos, atlas = 0, atlasPos = tile3_atlasPos },
      new CellData { layer = 0, pos = tile4_pos, atlas = 0, atlasPos = tile4_atlasPos },
      ...
  };
  tileMap.SetCells(cellData);

• set_area - allows for passing data for updating a rectangular area (chunk) of the tile map. Data would take a form of a 2-dimensional array or something. This would offer the most room for optimizations.

would yield a number of benefits:

• Passing a list of cells to update at the same time equals to reducing the need for multiple calls between scripting runtime and the actual Godot implementation - better performance
• There would be multiple opportunities for additional optimizations as Godot's internal code can handle the larger chunk of data more optimally

[Calinou]

Thanks for the proposal! Consolidating in #1538.