fix(ads-client): change MozAdsTelemetry from with_foreign to callback_interface

MozAdsTelemetry is always implemented by the foreign side (JS/Kotlin/Swift)
and is only ever passed from foreign code to Rust — never the other way around.
callback_interface is the correct semantic for this pattern and enables the
geckojs uniffi-bindgen-gecko-js pipeline to generate FireAndForget vtable
handlers, avoiding a deadlock where Rust calls telemetry methods synchronously
from within a callSync on the JS main thread.

Author: Almaju

components/ads-client/src/ffi.rs

@@ -157,8 +157,8 @@ impl MozAdsClientBuilder {
         self
     }
 
-    pub fn telemetry(self: Arc<Self>, telemetry: Arc<dyn MozAdsTelemetry>) -> Arc<Self> {
-        self.0.lock().telemetry = Some(telemetry);
+    pub fn telemetry(self: Arc<Self>, telemetry: Box<dyn MozAdsTelemetry>) -> Arc<Self> {
+        self.0.lock().telemetry = Some(Arc::from(telemetry));
         self
     }
 }

components/ads-client/src/ffi/telemetry.rs

@@ -12,7 +12,7 @@ use crate::http_cache::{CacheOutcome, HttpCacheBuilderError};
 use crate::mars::error::{RecordClickError, RecordImpressionError, ReportAdError};
 use crate::telemetry::Telemetry;
 
-#[uniffi::export(with_foreign)]
+#[uniffi::export(callback_interface)]
 pub trait MozAdsTelemetry: Send + Sync {
     fn record_build_cache_error(&self, label: String, value: String);
     fn record_client_error(&self, label: String, value: String);