[refactor] Replace deprecated curve.IsOnCurve low-level API with crypto/ecdh for NIST curve validation and ECDH operations.

[Unique-Divine]

From the Compiler

x/evm/precompile/p256.go|89 col 11| curve.IsOnCurve is deprecated: this is a
low-level unsafe API. For ECDH, use the crypto/ecdhpackage. The NewPublicKey
methods of NIST curves in crypto/ecdh acceptthe same encoding as the Unmarshal
function, and perform on-curve checks.

[Unique-Divine]

Updated patterns for avoiding that function seem more complex than using what we have now. Closing as unnecessary