test(s2n-quic): verify connection success/failure when mTLS is required

[toidiu]

Description of changes:

This PR adds some integration testing around connection establishment when mTLS negotiation is required. There are two test:

• happy-path: test when mTLS is required and successful. We expect the handshake to complete and data to be sent/received
• failure-case: test when handshake fails specifically due to failed client-certficat-auth (mTLS). We expect client TLS handshake to succeed but the Quic handshake to fail. We also expect the server handshake to fail. Finally we expect that no data is sent by the server.

Call-outs:

• I include some new certs for testing mTLS. These certs were generated using the script in examples/rustls-mtls. I considered modifying the rustls-mtls example to use the new certs in s2n-quic-core but the changes were getting large for minimal gain (since its testing certs)
• An example already exists for using mTLS with rustls.
• I created an issue to add testing for rustls since we might want to make it easier to enable mTLS for rustls also. Add mTLS testing for rustls #1726

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[toidiu]

So I choose the max_handshake / 2 after some experimentation. Its hard to pinpoint the sleep duration since there seems to be some interplay between the network delay, sleep and max handshake duration.

However, since we are testing all the various combinations I think it sets a good baseline for us to work from. Thoughts?

[toidiu]

Spoke offline. The delay and loss wasnt providing much value and I decided to remove it. Instead I added a success and failure case for mTLS testing.

[camshaft]

I was really hoping to have the failure test to show that the server doesn't even accept the connection and yield to the application at all. Here's my recommended changes:
mtls.patch