random-util: rename acquire_random_bytes() → genuine_random_bytes()

It's more descriptive, since we also have a function random_bytes()
which sounds very similar.

Also rename pseudorandom_bytes() to pseudo_random_bytes(). This way the
two functions are nicely systematic, one returning genuine random bytes
and the other pseudo random ones.

src/libsystemd/sd-id128/sd-id128.c

@@ -272,7 +272,7 @@ _public_ int sd_id128_randomize(sd_id128_t *ret) {
 
         assert_return(ret, -EINVAL);
 
-        r = acquire_random_bytes(&t, sizeof t, true);
+        r = genuine_random_bytes(&t, sizeof t, true);
         if (r < 0)
                 return r;