storcon: silence cplane 404s on tenant creation (#10665)

## Problem

We get WARN log noise on tenant creations. Cplane creates tenants via
/location_config. That returns the attached locations in the response
and spawns a reconciliation which will also attempt to notify cplane. If
the notification is attempted before cplane persists the shards to its
database, storcon gets back a 404. The situation is harmless, but
annoying.

## Summary of Changes

* Add a tenant creation hint to the reconciler config
* If the hint is true and we get back a 404 on the notification from
cplane, ignore the error, but still queue the reconcile up for a retry.

Closes https://github.com/neondatabase/cloud/issues/20732

storage_controller/src/compute_hook.rs

@@ -225,7 +225,7 @@ pub(crate) enum NotifyError {
     // We shutdown while sending
     #[error("Shutting down")]
     ShuttingDown,
-    // A response indicates we will never succeed, such as 400 or 404
+    // A response indicates we will never succeed, such as 400 or 403
     #[error("Non-retryable error {0}")]
     Fatal(StatusCode),