feat: Support infinite maps in flame_tiled

[ufrshubham]

Description

Stacked on #4073, which upgrades flame_tiled to tiled 0.12.0.

Adds support for infinite maps from the Tiled editor.

Until now, loading an infinite map crashed with a null check error. Infinite maps don't have a
single tileData grid. Tiled stores their tiles in chunks, usually 16×16, placed at any tile
coordinate, including negative ones when you paint left of or above the origin. flame_tiled
assumed a width × height grid starting at (0, 0) everywhere: cacheTiles() started with
layer.tileData!, and cached transforms were indexed as transforms[x][y].

This PR builds on the new TileLayer tile access APIs from flame-engine/tiled.dart#94
(contentBounds, tileAt, setTileAt, forEachTile), which work the same way for finite and
infinite layers.

Tile layers (FlameTileLayer and the four orientation layers):

• The transform cache now covers the layer's contentBounds: (0, 0, width, height) for finite
  layers, and the area covered by all chunks for infinite ones. Transforms are stored relative to
  that area's top-left corner (originX/originY), so negative coordinates work. transformAt
  and storeTransform do the offset, so nothing indexes the cache directly anymore.
• Tiles are painted in row order: rows sorted by y, each row sorted by x, through
  tilesByWorldRow(). This matters because infinite layers store tiles chunk by chunk. Painting
  them in that order would draw all of one chunk before the first row of the chunk next to it.
  Tiles that overlap their neighbours (isometric, staggered, hexagonal and oversized tiles) would
  then stack wrongly along chunk borders. Finite maps are visited in the same order as before, so
  they render exactly the same.

RenderableTiledMap:

• getTileData/setTileData (and the ByLayerIndex variants) use TileLayer.tileAt/
  setTileAt. They take the tile coordinates shown in the Tiled editor, so negative coordinates
  work on infinite maps. For cells outside the map (or outside every chunk), getTileData returns
  null and setTileData does nothing. Before, both threw a RangeError for cells outside a
  finite map.
• tileStack uses transformAt, so it also works at negative coordinates.

Current limitations (also documented in tiled.md):

• All chunks in the file are cached at load time. Streaming chunks based on the camera isn't
  implemented yet.
• TiledComponent's size still comes from the map's width and height, so tiles at negative
  coordinates render outside the component's bounds.
• setTileData can't create new chunks.

Tests:

• Loading an empty infinite map, and reading, writing and tileStack at negative coordinates.
• Three goldens, rendered with a new renderMapRegionToPng helper that can capture negative
  coordinates:
  • infinite_map.png: a whole infinite map, with two layers across six chunks.
  • infinite_oversized_tiles_orthogonal.png: a dungeon room across the chunk border at x = 0,
    with a 32×32 door standing in front of the top wall, so its frame overlaps the walls of both
    chunks. I checked that this golden fails if tiles are painted chunk by chunk: the wall of the
    right chunk then covers half the door.
  • infinite_oversized_tiles_isometric.png: an isometric scene across the four chunks around the
    origin.

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [-] I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

Closes #2855
Closes #3932

[spydon]

Nice, lgtm!
It was surprisingly little code to solve that.