[FEATURE] fix undefined behavior in BitCurve.Add

[YoshihitoAso]

Is your feature request related to a problem? Please describe.

The currently used secp256 module still has bugs that have been fixed in the latest go-ethereum.
For details, see the go-ethereum PR below.

• crypto/secp256k1: fix undefined behavior in BitCurve.Add ethereum/go-ethereum#22621

Describe the solution you'd like

I would like to port the above PR fix.