wNAF, wNAFUnsafe: merge some logic, remove duplicate code

[paulmillr]

This code part is sensitive, because it handles private keys.

TODO:

• Investigate how precomputeMSMUnsafe can be simplified as well
• same for pippenger
• Investigate zero addition in "It's not obvious how this can fail, but still worth investigating later."
  • Seems like infinity point can easily be created
  • Fake points are created using predictable pattern: they fetch [offsetF1.neg(), offsetF2, offsetF3.neg(), offsetF4...] where offsetF = window*windowSize
  • This means we can construct a scalar which would trigger the conditions

Mirroring to:

• paulmillr/noble-secp256k1@47cb166
• paulmillr/noble-ed25519@6d54433