SslStream.IsMutuallyAuthenticated calls are expensive on Windows #95687
Description
On Windows, client SslStream instances need to check if the client certificate was used via native API to SSPI. This call seems to be quite expensive if user calls the property getter often (e.g. for audit logging ber HTTP/2 request).
We should consider doing some internal caching since the value of the property should not change during the lifetime of the SslStream instance, with an exception of post-handshake client certificate negotiation.