share/ipld: Remove duplicated namespace appended by NMTWrapper

[renaynay]

Context

The NMTWrapper in celestia-core prepends to share (leaf nodes) an additional namespace, which is just a copy of real namespaces or the constant parity namespace.

Goal

Optimize data storage and network by removing this additional prepended namespace and automatically prepend it where needed.

Refs

celestiaorg/nmt#55 (comment)

[Wondertan]

Unfortunately, we cannot implement this(in a clean way without introducing additional complexity).

If we want to cut the additional namespace added by NMTWrapper, then we should add it back once we receive it from the network so that we can properly verify the integrity. Doing this requires namespaceHasher to know from which quadrant the share data is coming, which is not possible