accounts/abi: fix MakeTopics mutation of big.Int inputs

[jmank88]

#28764 updated func MakeTopics to support negative *big.Ints. However, it also changed the behavior of the function from just reading the input *big.Int via Bytes(), to leveraging big.U256Bytes which is documented as being destructive:

go-ethereum/common/math/big.go

Lines 175 to 177 in a5fe735

	// U256Bytes converts a big Int into a 256bit EVM number.
	// This operation is destructive.
	func U256Bytes(n *big.Int) []byte {

This was flagged by the race detector in our test suite, due to sharing some fixture variables for "constants" like oneEth. Looking around the codebase, other users of this function make defensive copies, like packNum:

go-ethereum/accounts/abi/pack.go

Line 81 in 2814ee0

return math.U256Bytes(new(big.Int).Set(value.Interface().(*big.Int)))

This PR updates MakeTopics to make a copy in the same way.

[MariusVanDerWijden]

SGTM

[rjl493456442]

LGTM,

can you also fix here? https://github.com/ethereum/go-ethereum/blob/master/signer/core/apitypes/types.go#L679

[jmank88]

LGTM,

can you also fix here? master/signer/core/apitypes/types.go#L679

Done

[holiman]

LGTM