fix(s2n-tls-hyper): Add proper IPv6 address formatting

[goatgoose]

Description of changes:

s2n-tls-hyper provides s2n-tls-tokio with a server name by parsing the host out of the URI for an HTTP request. s2n-tls uses the http::uri:::Uri::host() API to do this:

s2n-tls/bindings/rust/s2n-tls-hyper/src/connector.rs

Line 122 in 9877437

let host = req.host().unwrap_or("").to_owned();

Per RFC 3986, IPv6 addresses are enclosed with square brackets in the host section of a URI:
https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2

   IP-literal = "[" ( IPv6address / IPvFuture  ) "]"

The value returned by the Uri::host() API includes these square brackets. While the square brackets are part of the "host" URI content, they aren't part of the actual address, and should not be sent in the server name or matched against identities in the server's certificate. This PR trims out these square brackets so that s2n-tls-tokio is provided the proper server name when an IPv6 address is specified in an HTTP request.

Call-outs:

None

Testing:

A new test was added that uses a certificate with an IPv6 identity to check that the server name is properly formatted. This test also generally tests s2n-tls-hyper connecting to an IPv6 endpoint.

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

[goatgoose]

Certificate content:

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            4f:58:57:a5:76:45:86:96:de:ab:a5:24:6e:a9:67:38:a0:1e:52:8a
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, ST=MA, L=Boston, O=Amazon, OU=AmazonWebServices, CN=localhost
        Validity
            Not Before: Nov 26 04:52:47 2024 GMT
            Not After : Nov  2 04:52:47 2124 GMT
        Subject: C=US, ST=MA, L=Boston, O=Amazon, OU=AmazonWebServices, CN=localhost
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    ...
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Key Identifier: 
                4E:BE:C7:F2:CF:FC:A3:6C:A4:A4:A3:B8:E6:3B:EC:A1:BE:BB:F7:80
            X509v3 Authority Key Identifier: 
                4E:BE:C7:F2:CF:FC:A3:6C:A4:A4:A3:B8:E6:3B:EC:A1:BE:BB:F7:80
            X509v3 Basic Constraints: critical
                CA:TRUE
            X509v3 Subject Alternative Name: 
                IP Address:0:0:0:0:0:0:0:1
    Signature Algorithm: sha256WithRSAEncryption
    Signature Value:
        ...