CmptLoader

Splits a Composite (cmpt) container into its inner tiles. The format is:

16-byte CmptHeader
for i in 0..tilesLength:
  inner tile (its own b3dm / i3dm / pnts / cmpt with its own header)

Each inner tile's byteLength field (at offset +8 from the inner tile's start) drives how many bytes to slice for that sub-payload.