Improve Kerberos SSPI and GSSAPI Related Issues

> Note: This change might be breaking. Confidentiality and integrity is not implied anymore. User needs to actively specify these two flag to get sign and seal.

Don't you always want confidentiality and integrity by default, you should only not be setting it if the NO_INTEGRITY flag is specified.

> It looks good to me, I'm surprised it has worked so far. We'll need to test that it doesn't break things for other protocols though

AFAIK LDAP (when using LDAPS or LDAP + StartTLS) is the only one that has needed this and specifically with the `GSS-SPNEGO` SASL. I've not encountered any other protocols so far that requires explicitly disabling integrity/confidentiality with the auth.

_Originally posted by @jborean93 in https://github.com/Devolutions/sspi-rs/issues/189#issuecomment-1864992527_

integrity should be implied while confidentiality is a choice (i.e when use without TLS). Also, these two flags should be effective while encrypt/decrypt the messages.