EIP-2681 compliance - fail CREATE/CREATE2 at nonce max uint64-1

[Cordtus]

Changes

• Add guard in core/vm/evm.go:create - if creator nonce == math.MaxUint64 ⇒ return (nil, addr{}, gas, ErrNonceMax) before any side effects.
• core/vm/errors.go: add ErrNonceMax. No opcode changes needed (errors already push 0).
• Tests: top-level and internal create fail at 2⁶⁴−1 (full child gas returned); boundary at 2⁶⁴−2 succeeds and increments.
• Addresses Issue #400
• EIP-2681 referene

Testing

# Top-level create must fail at nonce==2^64-1 (no initcode gas)
go test ./core/vm -run TestCreate_TopLevel_MaxNonce -v

# Internal CREATE must fail at nonce==2^64-1 (pushes 0; no side effects)
go test ./core/vm -run TestCreate_Internal_MaxNonce -v

# Boundary: nonce==2^64-2 succeeds, increments to 2^64-1
go test ./core/vm -run TestCreate_Boundary_SucceedsAtMaxMinus1 -v