Switch on --timelines-onto-safekeepers in integration tests (#11712)

Switch on the `--timelines-onto-safekeepers` param in integration tests.
Some changes that were needed to enable this but which I put into other
PRs to not clutter up this one:

* #11786
* #11854
* #12129
* #12138

Further fixes that were needed for this:

* https://github.com/neondatabase/neon/pull/11801
* https://github.com/neondatabase/neon/pull/12143
* https://github.com/neondatabase/neon/pull/12204

Not strictly needed, but helpful:

* https://github.com/neondatabase/neon/pull/12155

Part of #11670
Closes #11424

test_runner/fixtures/neon_fixtures.py

@@ -489,7 +489,9 @@ class NeonEnvBuilder:
         self.config_init_force: str | None = None
         self.top_output_dir = top_output_dir
         self.control_plane_hooks_api: str | None = None
-        self.storage_controller_config: dict[Any, Any] | None = None
+        self.storage_controller_config: dict[Any, Any] | None = {
+            "timelines_onto_safekeepers": True,
+        }
 
         # Flag to enable https listener in pageserver, generate local ssl certs,
         # and force storage controller to use https for pageserver api.
@@ -4909,6 +4911,9 @@ class Safekeeper(LogUtils):
         log.info(f"finished pulling timeline from {src_ids} to {self.id}")
         return res
 
+    def safekeeper_id(self) -> SafekeeperId:
+        return SafekeeperId(self.id, "localhost", self.port.pg_tenant_only)
+
     @property
     def data_dir(self) -> Path:
         return self.env.repo_dir / "safekeepers" / f"sk{self.id}"