Refactor balance fetching

[sl1depengwyn]

blockscout/apps/ethereum_jsonrpc/lib/ethereum_jsonrpc/contract.ex

Lines 78 to 81 in f2d7bd4

	rescue
	error ->
	Enum.map(requests, fn _ -> format_error(error) end)
	end

here we put error on all calls if we see it in a single call thus harming performance, we should put errors individually only to calls that actually errored