Switch to rustls and webpki-roots (#30025)

This change replaces OpenSSL with rustls and also the manually curated
CA certs file with webpki-roots (effectively the same thing, but as a
crate).

Generally speaking the design of the network stack is the same. Changes:

- Code around certificate overrides needed to be refactored to work with
  rustls so the various thread-safe list of certificates is refactored
  into `CertificateErrorOverrideManager`
- hyper-rustls takes care of setting ALPN protocols for HTTP requests,
  so for WebSockets this is moved to the WebSocket code.
- The safe set of cypher suites is chosen, which seem to correspond to
  the "Modern" configuration from [1]. This can be adjusted later.
- Instead of passing a string of PEM CA certificates around, an enum is
  used that includes parsed Certificates (or the default which reads
  them from webpki-roots).
- Code for starting up an SSL server for testing is cleaned up a little,
  due to the fact that the certificates need to be overriden explicitly
  now. This is due to the fact that the `webpki` crate is more stringent
  with self-signed certificates than SSL (CA certificates cannot used as
  end-entity certificates). [2]

1. https://wiki.mozilla.org/Security/Server_Side_TLS
2. https://github.com/briansmith/webpki/issues/114

Fixes #7888.
Fixes #13749.
Fixes #26835.
Fixes #29291.

resources/badcert.html

@@ -6,7 +6,7 @@
   <p>${reason}</p>
   <button id="leave" onclick="history.back()">Go back (recommended)</button>
   <button id="allow">Allow certificate temporarily</button>
-  <pre id="bytes">${bytes}</pre>
+  <div style="word-break: break-all; font-family: monospace" id="bytes">${bytes}</div>
   <script>
     let bytes = document.getElementById('bytes').textContent;
     let button = document.getElementById('allow');
@@ -18,7 +18,7 @@
             xhr.onloadend = function() {
                 location.reload(true);
             };
-            xhr.send("${secret}&" + btoa(bytes));
+            xhr.send("${secret}&${bytes}");
         };
     } else {
         button.style.display = "none";