ipld: Consolidate parameters used for square size.

[renaynay]

In the IPLD plugin, there's a parameter extendedRowOrColumnSize hardcoded (to avoid importing the const) at 2*128 which was chosen arbitrarily likely because it's reasonable (somewhere around 1-4 MB). It's important that the parameters aren't different in other parts the celestia codebases.

Ref

[Wondertan]

This should be resolved together with refactoring supporting the move to a new ipld related stuff repo #21 or #111

[renaynay]

Yeah let's link to this issue in #21 as a TODO item, it will look nice.