getTileHolder
Searches this holder's own subtree (this tile, then depth-first through tiles) for the TileHolder whose id equals tileId.
Return
the matching TileHolder, or null if tileId isn't found in this subtree.
Parameters
tileId
the id to search for.
includeEventsOnSearch
when true and the id isn't found among tiles, also searches inside events — needed because a tile can live nested under an event's own tiles (e.g. one added via AddTiles, which is itself reachable through an EventHolder). Most callers leave this false; TilesManager.updateTile/checkIfTileHasChildren/getTileChildrenCount pass true.