Since 8198423, we have a bit of redundancy:

- get_chunk_type_by_size(size, is_class) and ChunkManager::list_index().
- get_size_for_nonhumongous_chunktype() and ChunkManager::size_by_index()

Since the new get_.. functions are more versatile (usable without a ChunkManager instance), they should be kept. The ChunkManager methods should be removed or reimplemented using the get_... functions.

Also, 8198423 accidentally removed the ChunkManager list_index gtest, which should be reinstantiated.