[QUIC] Split out MsQuic configuration from connection

[scalablecory]

An MsQuic configuration allocates a number of resources that are able to be shared between multiple connections.

Currently, we are sharing a configuration on server connections, but are allocating a new one per client-initiated connection. We should consider breaking this out into its own API so that e.g. the SocketsHttpHandler connection pools can have a single configuration.

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[geoffkizer]

What settings/resources are associated with an msquic session?

[scalablecory]

According to docs:

Primarily, this consists of the ALPN string used for the connection handshakes and TLS state used for session resumption.

@nibanks anything else interesting to consider? Why would we ever want to have separate sessions (beyond different ALPN strings)?

[nibanks]

The MsQuic "session" object is completely going away. I'd just close this issue. See this PR for more details: microsoft/msquic#777

[scalablecory]

This would look something like:

QuicClientConnectionOptions options = ...;
EndPoint endPoint = ...;

using QuicClientConfiguration clientConfig = await QuicConfiguration.CreateAsync(options, cancellationToken);
using QuicConnection connection = await QuicConnection.ConnectAsync(clientConfig, endPoint, cancellationToken);