Expose Parameter for TLS Provider

[nibanks]

Description

Fixes #2761. Adds a new parameter that can be called via GetParam to query the compiled in TLS provider. This allows application code to handle any TLS provider specific differences.

cc @rzikm

Testing

Added get/set test.

Documentation

Updated for new parameter.

[GF-Huang]

Is this means .NET 7 QUIC classes can work on older Win10 even if Win7? For the QUIC namespaces docs, I can't see any description about this.

[rzikm]

Is this means .NET 7 QUIC classes can work on older Win10 even if Win7? For the QUIC namespaces docs, I can't see any description about this.

We don't have test coverage for running with OpenSSL-based MsQuic on Windows, but last time I tried it it worked (after integrating the change from this PR). It is not officially supported, but we are considering official support in 8.0. If you find any issues, feel free to raise a PR in dotnet/runtime repo.

The only pitfall of OpenSSL on Windows I can remember now is that any certificates you use must be exportable, because we need to serialize them to memory in order to pass them to MsQuic.