Investigate failing auto-tests (QSslSocket et. al with OpenSSL v3)

With OpenSSL v3 as a TLS backend some auto-tests started failing:

• tst_QSslSocket::protocolServerSide (error:0A00018E:SSL routines::ca md too weak - replacing the old cert fixes the problem).
• tst_QSslSocket::serverCipherPreferences (error:0A000076:SSL routines::no suitable signature algorithm) - test seems to be crap and very OpenSSL version specific. e.g. I can make it work if selecting TLS_CHACHA20_POLY1305_SHA256 as the preferable ciphersuite ... others don't seem work though, have to remove/re-think the test).
• tst_QSslSocket::setLocalCertificateChain (the problem with 'weak' MD, same as in 'protoccolServerSide')
• tst_QSslSocket::setSocketDescriptor (same problem with old cert/MD)
• tst_QSslSocket::allowedProtocolNegotiation (error:0A00018E:SSL routines::ca md too weak)
• tst_QSslSocket::spontaneousWrite (old cert, MD)
• tst_QSslSocket::verifyMode() - TBU
• tst_QSslSocket::setReadBufferSize (error:0A00018E:SSL routines::ca md too weak)
• tst_QSslSocket::abortOnSslErrors (error:0A00018E:SSL routines::ca md too weak)
• tst_QSslSocket::waitForMinusOne (TBU)
• tst_QSslSocket::qtbug18498_peek2 (TBU)
• tst_QSslSocket::dhServer (error:0A00018E:SSL routines::ca md too weak)
• tst_QSslSocket::dhServerCustomParams (error:0A00018E:SSL routines::ca md too weak)
• tst_QSslSocket::ecdhServer (error:0A00018E:SSL routines::ca md too weak)
• tst_QSslSocket::verifyClientCertificate (old cert, MD)
• tst_QSslSocket::ephemeralServerKey (old cert, MD)
• tst_QSslSocket::oldErrorsOnSocketReuse (MD problem)
• tst_QSslSocket::alertInvalidCertificate(MD)

MD == "ca md too weak"