Consolidate the locations where we have our internal perl modules

Instead of having perl modules under test/testlib and util,
consolidate them all to be inside util/perl.

(this is an adaptation of the part of #4069 that wasn't included in #4666)

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4667)