Fix task leak on config entry unload/retry

[bdraco]

Proposed change

Since the task was added to self._tasks without a task.add_done_callback(self._tasks.remove) each unload/retry would leak a new set of tasks.

Depending on how often config entries reloaded or retried this was a slow leak or a fast one. In my case it was a slow leak because I only had one config entry that was retrying over and over again. See the profile in #96980 for more details.

regressed in #91531

fixes #96980 likely also fixes #93713

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[bdraco]

manually confirmed leak is gone with

@@ -696,9 +696,16 @@ class ConfigEntry:
         for task in self._background_tasks:
             task.cancel(cancel_message)
 
-        _, pending = await asyncio.wait(
-            [*self._tasks, *self._background_tasks], timeout=10
+        tasks = [*self._tasks, *self._background_tasks]
+        if tasks:
+            _LOGGER.warning(
+                "Config entry %s with domain %s is being unloaded, waiting for tasks: %s, background tasks: %s",
+                self.entry_id,
+                self.domain,
+                self._tasks,
+                self._background_tasks,
             )
+        _, pending = await asyncio.wait(tasks, timeout=10)
 
         for task in pending:
             _LOGGER.warning(
@@ -917,7 +924,17 @@ class ConfigEntriesFlowManager(data_entry_flow.FlowManager):

tasks no longer build up