Slow batch KZG verification during range sync

[jimmygchen]

I noticed we don't use rayon for batch kzg verification, so this could be quite slow at high blob count
for each supernodes range batch at 48 blobs, that's 508ms * 32 = 16,256ms (we're not using rayon)

This applies to range sync, I'm not sure if we've applied KZG validation to backfill yet. Will investigate.

[jimmygchen]

EDIT: ignore the numbers below, I think it might be due to the limited CPU on my laptop and it's struggling with the spamoor computing proofs for 32 blobs per slot. I'll retest without spamoor running.

---

Some current numbers - gossip verifying a single data column containing 32 cells took 226ms and verify KZG took 171ms:

This would be way worse during range sync as we don't use rayon at all for this so number grow pretty much linearly - a beacon node with a single validator attached would have to verify have 8 columns * 32 slots = 256 columns per range sync batch.

[jimmygchen]

Completed in #7921