libs/common: Refactor libs/common 4 (#4237)

* libs/common: Refactor libs/common 4

- move byte function out of cmn to its own pkg
- move tempfile out of cmn to its own pkg
- move throttletimer to its own pkg

ref #4147

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add changelog entry

* fix linting issues

libs/bytes/byteslice.go

@@ -0,0 +1,10 @@
+package bytes
+
+// Fingerprint returns the first 6 bytes of a byte slice.
+// If the slice is less than 6 bytes, the fingerprint
+// contains trailing zeroes.
+func Fingerprint(slice []byte) []byte {
+	fingerprint := make([]byte, 6)
+	copy(fingerprint, slice)
+	return fingerprint
+}