[TBD][ALGEBRA] Implement Matrix struct and its operations

[FoodChain1028]

Description

Implement a Matrix structure that represent the Matrix $A$, $B$, $C$ and $D$ in the paper.

TODOs

• Implement a matrix structure (this is a vector of vector)
  • M.row(int) which returns the value of row[i]
  • M.col(int) which returns the value of col[i]
• Implement matrix operations with other structure
  • Matrix * Matrix
  • Matrix * polynomial_ring_vector
  • Matrix * scalar