all: simplify timestamps to uint64 (#19372)

* all: simplify timestamps to uint64

* tests: update definitions

* clef, faucet, mobile: leftover uint64 fixups

* ethash: fix tests

* graphql: update schema for timestamp

* ethash: remove unused variable

consensus/ethash/consensus_test.go

@@ -76,7 +76,7 @@ func TestCalcDifficulty(t *testing.T) {
 		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
 		diff := CalcDifficulty(config, test.CurrentTimestamp, &types.Header{
 			Number:     number,
-			Time:       new(big.Int).SetUint64(test.ParentTimestamp),
+			Time:       test.ParentTimestamp,
 			Difficulty: test.ParentDifficulty,
 		})
 		if diff.Cmp(test.CurrentDifficulty) != 0 {