elliptic curve point (a.k.a. pubkey) to derive remotepubkey. This is static for each channel and it is negotiated during channel opening. We don't want to use same pubkeys for each commitments more than once, so the key derivation needs new PerCommitmentPoint for each HTLCs. see bolt03 for more detail.

In case of option_static_remotekey feature bit is negotiated, this corresponds to remotepubkey which the public key that counterparty gets paid to when the channel closes.