Log the original bind exception when encountering Failed to listen on 0.0.0.0, continuing because listening on [::] (#19297)

**Before:**

```
WARNING - call_when_running - Failed to listen on 0.0.0.0, continuing because listening on [::]
```

**After:**

```
WARNING - call_when_running - Failed to listen on 0.0.0.0, continuing because listening on [::]. Original exception: CannotListenError: Couldn't listen on 0.0.0.0:8008: [Errno 98] Address already in use.
```

changelog.d/19297.misc

@@ -0,0 +1 @@
+Log the original bind exception when encountering `Failed to listen on 0.0.0.0, continuing because listening on [::]`.

synapse/app/__init__.py

@@ -54,7 +54,9 @@ def check_bind_error(
     """
     if address == "0.0.0.0" and "::" in bind_addresses:
         logger.warning(
-            "Failed to listen on 0.0.0.0, continuing because listening on [::]"
+            "Failed to listen on 0.0.0.0, continuing because listening on [::]. Original exception: %s: %s",
+            type(e).__name__,
+            str(e),
         )
     else:
         raise e