Make TAP::Harness and TAP::Parser optional.

In OpenSSL 1.1.1 the script run_tests.pl has an effectiver
workaround to fall back to Test::Harness, if TAP::Harness
is not available. That code has substantially changed,
but it seems it should still fall back but doesn't.

Observed on SuSE Linux Enterprise Server 11 (SLES11).

Error messages:

Can't locate TAP/Parser.pm in @inc (@inc contains: /path/to/bld/openssl300/test/../util/perl /path/to/local/perl/lib/perl5 /usr/lib/perl5/5.10.0/x86_64-linux-thread-multi /usr/lib/perl5/5.10.0 /usr/lib/perl5/site_perl/5.10.0/x86_64-linux-thread-multi /usr/lib/perl5/site_perl/5.10.0 /usr/lib/perl5/vendor_perl/5.10.0/x86_64-linux-thread-multi /usr/lib/perl5/vendor_perl/5.10.0 /usr/lib/perl5/vendor_perl .) at /path/to/local/perl/lib/perl5/parent.pm line 20.
BEGIN failed--compilation aborted at /path/to/bld/openssl300/test/run_tests.pl line 131.

and

Can't locate TAP/Harness.pm in @inc (@inc contains: /path/to/bld/openssl300/test/../util/perl /path/to/local/perl/lib/perl5 /usr/lib/perl5/5.10.0/x86_64-linux-thread-multi /usr/lib/perl5/5.10.0 /usr/lib/perl5/site_perl/5.10.0/x86_64-linux-thread-multi /usr/lib/perl5/site_perl/5.10.0 /usr/lib/perl5/vendor_perl/5.10.0/x86_64-linux-thread-multi /usr/lib/perl5/vendor_perl/5.10.0 /usr/lib/perl5/vendor_perl .) at /path/to/local/perl/lib/perl5/parent.pm line 20.
BEGIN failed--compilation aborted at /path/to/bld/openssl300/test/run_tests.pl line 215.

Concerning the fix: the docs for parent.pm show, that without
the "-norequire" it puts the require statement in a BEGIN block
which probably runs before the eval, to the loading is no
longer encapsulated by the eval. Without the additional require
line, the loading doesn't happen at all, so the availability
testing fails. Combining the "-norequire" and an explicit
"require" worked for me.

Tested on the original problem platform SLES 11, but also on
SLES 12 and 15, RHEL 6, 7 and 8 plus Solaris 10 Sparc.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from #12500)

test/run_tests.pl

@@ -148,7 +148,8 @@ sub find_matching_tests {
 
 $eres = eval {
     package TAP::Parser::OpenSSL;
-    use parent 'TAP::Parser';
+    use parent -norequire, 'TAP::Parser';
+    require TAP::Parser;
 
     sub new {
         my $class = shift;
@@ -231,7 +232,8 @@ sub find_matching_tests {
     }
 
     package TAP::Harness::OpenSSL;
-    use parent 'TAP::Harness';
+    use parent -norequire, 'TAP::Harness';
+    require TAP::Harness;
 
     package main;