pageserver: more permissive activation timeout when testing (#6564)

## Problem

The 5 second activation timeout is appropriate for production
environments, where we want to give a prompt response to the cloud
control plane, and if we fail it will retry the call. In tests however,
we don't want every call to e.g. timeline create to have to come with a
retry wrapper.

This issue has always been there, but it is more apparent in sharding
tests that concurrently attach several tenant shards.

Closes: https://github.com/neondatabase/neon/issues/6563

## Summary of changes

When `testing` feature is enabled, make `ACTIVE_TENANT_TIMEOUT` 30
seconds instead of 5 seconds.

pageserver/src/http/routes.rs

@@ -79,8 +79,14 @@ use utils::{
 // For APIs that require an Active tenant, how long should we block waiting for that state?
 // This is not functionally necessary (clients will retry), but avoids generating a lot of
 // failed API calls while tenants are activating.
+#[cfg(not(feature = "testing"))]
 const ACTIVE_TENANT_TIMEOUT: Duration = Duration::from_millis(5000);
 
+// Tests run on slow/oversubscribed nodes, and may need to wait much longer for tenants to
+// finish attaching, if calls to remote storage are slow.
+#[cfg(feature = "testing")]
+const ACTIVE_TENANT_TIMEOUT: Duration = Duration::from_millis(30000);
+
 pub struct State {
     conf: &'static PageServerConf,
     tenant_manager: Arc<TenantManager>,