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.

components/script/dom/servoparser/mod.rs

@@ -36,6 +36,7 @@ use crate::dom::virtualmethods::vtable_for;
 use crate::network_listener::PreInvoke;
 use crate::realms::enter_realm;
 use crate::script_thread::ScriptThread;
+use base64::{engine::general_purpose, Engine as _};
 use content_security_policy::{self as csp, CspList};
 use dom_struct::dom_struct;
 use embedder_traits::resources::{self, Resource};
@@ -880,8 +881,8 @@ impl FetchResponseListener for ParserContext {
                     self.is_synthesized_document = true;
                     let page = resources::read_string(Resource::BadCertHTML);
                     let page = page.replace("${reason}", &reason);
-                    let page =
-                        page.replace("${bytes}", std::str::from_utf8(&bytes).unwrap_or_default());
+                    let encoded_bytes = general_purpose::STANDARD_NO_PAD.encode(&bytes);
+                    let page = page.replace("${bytes}", encoded_bytes.as_str());
                     let page =
                         page.replace("${secret}", &net_traits::PRIVILEGED_SECRET.to_string());
                     parser.push_string_input_chunk(page);