api: Flatten and simplify Servo preferences (#34966)

Flatten and simplify Servo's preferences code. In addition, have both
preferences and options passed in as arguments to `Servo::new()` and
make sure not to use the globally set preferences in `servoshell` (as
much as possible now).

Instead of a complex procedural macro to generate preferences, just
expose a very simple derive macro that adds string based getters and
setters.

- All command-line parsing is moved to servoshell.
- There is no longer the concept of a missing preference.
- Preferences no longer have to be part of the resources bundle because
  they now have reasonable default values.
- servoshell specific preferences are no longer part of the preferences
  exposed by the Servo API.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/net/hsts.rs

@@ -144,8 +144,8 @@ impl HstsList {
             return;
         }
 
-        let upgrade_scheme = if pref!(network.enforce_tls.enabled) {
-            if (!pref!(network.enforce_tls.localhost) &&
+        let upgrade_scheme = if pref!(network_enforce_tls_enabled) {
+            if (!pref!(network_enforce_tls_localhost) &&
                 match url.host() {
                     Some(Host::Domain(domain)) => {
                         domain.ends_with(".localhost") || domain == "localhost"
@@ -154,7 +154,7 @@ impl HstsList {
                     Some(Host::Ipv6(ipv6)) => ipv6.is_loopback(),
                     _ => false,
                 }) ||
-                (!pref!(network.enforce_tls.onion) &&
+                (!pref!(network_enforce_tls_onion) &&
                     url.domain()
                         .is_some_and(|domain| domain.ends_with(".onion")))
             {