chore: Miscellaneous optimizations

[kevaundray]

This makes the BatchToeplitz operations parallelized and also makes the fft parallelized and also iterative

[kevaundray]

This PR is mainly being used to figure out the magnitude to which parallelism helps -- if we want significant improvements, it will need to be in the MSM algorithm

[kevaundray]

Results -- baseline is single threaded master:

computing cells_and_kzg_proofs - NUM_THREADS: Single
                        time:   [180.78 ms 181.35 ms 182.08 ms]
                        change: [-10.891% -10.454% -10.017%] (p = 0.00 < 0.05)
                        Performance has improved.

computing cells_and_kzg_proofs - NUM_THREADS: Multi(4)
                        time:   [57.467 ms 57.642 ms 57.840 ms]
                        change: [-72.102% -71.859% -71.645%] (p = 0.00 < 0.05)
                        Performance has improved.

computing cells_and_kzg_proofs - NUM_THREADS: Multi(8)
                        time:   [40.380 ms 40.771 ms 41.192 ms]
                        change: [-81.162% -80.477% -79.991%] (p = 0.00 < 0.05)
                        Performance has improved.

computing cells_and_kzg_proofs - NUM_THREADS: Multi(16)
                        time:   [43.413 ms 43.995 ms 44.684 ms]
                        change: [-78.833% -78.526% -78.173%] (p = 0.00 < 0.05)
                        Performance has improved.

computing cells_and_kzg_proofs - NUM_THREADS: Multi(32)
                        time:   [49.036 ms 50.404 ms 52.169 ms]
                        change: [-76.070% -75.382% -74.463%] (p = 0.00 < 0.05)
                        Performance has improved.

Note: that the single threaded version has been improved because we the fft algorithm was changed.