pkg/p256k1/avx

• IMPLEMENTATION_PLAN.md
• avx_test.go
• debug_double_test.go
• field.go
• field_amd64.go
• field_amd64.s
• mulint_test.go
• point.go
• scalar.go
• scalar_amd64.go
• scalar_amd64.s
• trace_double_test.go
• types.go
• uint128.go
• uint128_amd64.go
• uint128_amd64.s