feat: add additional application context into Connection

[boquan-fang]

Goal

This PR changes the behavior of the set_application_context API to add multiple arbitrary application contexts which can be queried during handshakes. The definition of the app_context is changed from only accepting one application context to accept a map of application contexts.

Why

We are trying to allow s2n-quic to query the remote address information about the client during the handshake. This PR in s2n-tls allows that addressing information to be added with the connection.

How

Change the definition of the Context for the connection to be a HashMap of connection context. In this way, we can add as many application data as we want. Hence, we can add the remote address on top of context that were originally needed.

I also added a remove_application_context API to help users managing memory usage.

Callouts

I need to modify the memory_test's memory usage in order for this PR to pass the CI. My change involves changing a variable in the Context struct from Option to a HashMap which will definitely increase many usage by about 100 bytes per connection.

"/home/runner/work/s2n-tls/s2n-tls/bindings/rust/extended/s2n-tls/../../../../tests/pems/rsa_4096_sha512_client_cert.pem"
| stage               | total_blocks | total_bytes | curr_blocks | curr_bytes | max_blocks | max_bytes | test_pair_size |
|---------------------|--------------|-------------|-------------|------------|------------|-----------|----------------|
| ConnectionInit      | 134          | 64778       | 108         | 61578      | 84         | 19698     | 0              |
| AfterClientHello    | 149          | 91991       | 116         | 88406      | 92         | 46526     | 248            |
| AfterServerHello    | 353          | 170487      | 121         | 116773     | 123        | 102673    | 3524           |
| AfterClientFinished | 851          | 211414      | 257         | 108080     | 123        | 102673    | 3524           |
| HandshakeComplete   | 875          | 213526      | 256         | 90667      | 123        | 102673    | 3524           |
| ApplicationData     | 875          | 213526      | 256         | 90667      | 123        | 102673    | 3524           |
actual: 61578, expected: 61482
actual: 88406, expected: 88302

Refers to https://github.com/aws/s2n-tls/pull/5637/files#diff-63ac16ef5c47eee35caf3e2bbf1909d5a3062a8343d888d399eaf960acf7326b for the change.

Testing

This PR has unit tests for all new APIs it introduced. Also, I have implemented relevant changes for s2n-quic which can be found in aws/s2n-quic@main...boquan-fang:s2n-quic:get-ip-from-connection. s2n-quic's new_server_session API can now add the client's remote address into the connection.

Related

N/A

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

[WesleyRosenblum]

nice