replace `reed-solomon-erasure` dependency by `linalg` module

changelog

• add a one_less argument to field::merge_elements_into_bytes to mirror the one_more from field::split_data_into_field_elements
• add a linalg module which defines
  • a pub LinalgError enum
  • a pub(super) Matrix structure implement for any ark_ff::Field, e.g. <Bls12_381 as Pairing>::ScalarField
  • pub(super) Matrix::vandermonde
  • pub(super) Matrix::from_vec_vec
  • pub(super) Matrix::invert
  • pub(super) Matrix::mul
  • pub(super) Matrix::transpose
  • everything is tested extensively
• modify fec.rs to use linalg::Matrix instead of reed-solomon-erasure => tests still pass
• remove the dependency to reed-solomon-erasure completely