pageserver: add and stabilize import chaos test (#11982)

## Problem

Test coverage of timeline imports is lacking.

## Summary of changes

This PR adds a chaos import test. It runs an import while injecting
various chaos events
in the environment. All the commits that follow the test fix various
issues that were surfaced by it.

Closes https://github.com/neondatabase/neon/issues/10191

storage_controller/src/service.rs

@@ -3922,6 +3922,11 @@ impl Service {
         })
     }
 
+    #[instrument(skip_all, fields(
+        tenant_id=%req.tenant_shard_id.tenant_id,
+        shard_id=%req.tenant_shard_id.shard_slug(),
+        timeline_id=%req.timeline_id,
+    ))]
     pub(crate) async fn handle_timeline_shard_import_progress(
         self: &Arc<Self>,
         req: TimelineImportStatusRequest,
@@ -3971,6 +3976,11 @@ impl Service {
             })
     }
 
+    #[instrument(skip_all, fields(
+        tenant_id=%req.tenant_shard_id.tenant_id,
+        shard_id=%req.tenant_shard_id.shard_slug(),
+        timeline_id=%req.timeline_id,
+    ))]
     pub(crate) async fn handle_timeline_shard_import_progress_upcall(
         self: &Arc<Self>,
         req: PutTimelineImportStatusRequest,