time: move time.random() to time.misc module

avoids importing rand to programs that do not need pseudo random generation).

vlib/time/misc/misc_test.v

@@ -0,0 +1,17 @@
+import time.misc as tmisc
+import rand
+
+fn test_random() {
+	// guarantee CI test stability, by seeding the random number generator with a known seed
+	rand.seed(0)
+	t1 := tmisc.random()
+	t2 := tmisc.random()
+	t3 := tmisc.random()
+	t4 := tmisc.random()
+	assert t1.unix != t2.unix
+	assert t1.unix != t3.unix
+	assert t1.unix != t4.unix
+	assert t2.unix != t3.unix
+	assert t2.unix != t4.unix
+	assert t3.unix != t4.unix
+}