Add exit code test (refurbish p.r. 19152 for issue 19020)

[jkeenan]

This branch and p.r. exist in order to get come clean data on the problem originally described by @xsawyerx in https://github.com/Perl/perl5/issues/19020, who then submitted a p.r. in https://github.com/Perl/perl5/pull/19152. I have created new branch from that p.r., rebased on blead, with corrected MANIFEST,and titled it in order to trigger smoke-me tests.

[jkeenan]

This branch and p.r. exist in order to get come clean data on the problem originally described by @xsawyerx in #19020, who then submitted a p.r. in #19152. I have created new branch from that p.r., rebased on blead, with corrected MANIFEST,and titled it in order to trigger smoke-me tests.

I should have added: I expect several failures in the newly added test file, but once we see the scope of such failures we can decide how/whether to proceed.