Improve RSA test coverage.

Improve RSA test coverage.

MD5/SHA1 and MDC-2 have special-case logic beyond the generic DigestInfo
wrapping. Test that each of these works, including hash and length
mismatches (both input and signature). Also add VerifyRecover tests. It
appears 5824cc298174d462c827cd090675e30fc03f0caf added support for
VerifyRecover, but forgot to add the test data.

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #1474
(cherry picked from commit f320555735af7aa52172a2b8c56181445e8490dd)