collab: Add kill switches for syncing data to and from Stripe (#35304)

This PR adds two kill switches for syncing data to and from Stripe using
Collab.

The `cloud-stripe-events-polling` and `cloud-stripe-usage-meters-sync`
feature flags control whether we use Cloud for polling Stripe events and
updating Stripe meters, respectively.

When we're ready to hand off the syncing to Cloud we can enable the
feature flag to do so.

Release Notes:

- N/A

crates/collab/src/api/billing.rs

@@ -87,6 +87,14 @@ async fn poll_stripe_events(
     stripe_client: &Arc<dyn StripeClient>,
     real_stripe_client: &stripe::Client,
 ) -> anyhow::Result<()> {
+    let feature_flags = app.db.list_feature_flags().await?;
+    let sync_events_using_cloud = feature_flags
+        .iter()
+        .any(|flag| flag.flag == "cloud-stripe-events-polling" && flag.enabled_for_all);
+    if sync_events_using_cloud {
+        return Ok(());
+    }
+
     fn event_type_to_string(event_type: EventType) -> String {
         // Calling `to_string` on `stripe::EventType` members gives us a quoted string,
         // so we need to unquote it.
@@ -569,6 +577,14 @@ async fn sync_model_request_usage_with_stripe(
     llm_db: &Arc<LlmDatabase>,
     stripe_billing: &Arc<StripeBilling>,
 ) -> anyhow::Result<()> {
+    let feature_flags = app.db.list_feature_flags().await?;
+    let sync_model_request_usage_using_cloud = feature_flags
+        .iter()
+        .any(|flag| flag.flag == "cloud-stripe-usage-meters-sync" && flag.enabled_for_all);
+    if sync_model_request_usage_using_cloud {
+        return Ok(());
+    }
+
     log::info!("Stripe usage sync: Starting");
     let started_at = Utc::now();