Adds Schannel variants of SSLpinning tests that include the option
--ssl-revoke-best-effort to ignore certificate revocation check
failures which is required due to our custom test CA certificate.
Disable the original variants if the Schannel backend is enabled.
Also skip all IDN tests which are broken while using an msys shell.
This is a step to simplify test exclusions for Windows and MinGW.
Reviewed-by: Jay Satiro
Reviewed-by: Marcel Raad
Reviewed-by: Daniel Stenberg
Closes#7968
