hash: add wyhash + benchmark, add fnv1a, add u64.hex() (#3584)

vlib/hash/fnv1a/fnv1a_test.v

@@ -0,0 +1,9 @@
+import hash.fnv1a
+
+fn test_fnv1a() {
+	a := 'apple'
+	b := fnv1a.sum64_string(a)
+	c := fnv1a.sum64(a.bytes())
+	assert b.hex() == '0xf74a62a458befdbf'
+	assert c.hex() == '0xf74a62a458befdbf'
+}