SpMM Data Structures Bitmap implementation

[richard-syKim]

PR made solely for the purpose of sharing code for the meeting. Unless I make a crucial update, the code I will bring to the meeting will mostly be the same as it is here.

spmm-refine.jl and spmm-fin-mac.jl only had minor changes where I adjusted the way of measuring dense mat mul (using only a single thread) and finch tensors (utilizing column major), but I thought I would add the files just for your reference.

custom-imp.jl contains the bytemap implementation with slight modification after the last meeting and a new bitmap mat mul. The runtimes do improve relatively to other sparse data types as the density increases, but it still performs worse in general.