New hearing device pairing page: check gatt status

Checks the gatt status in `onConnectionStateChange()` and `onServiceDiscovered()` callbacks. Disconnects and removes the gatt from the `mConnectingGattList` if the gatt status is not success in these callbacks.

Bug: 307890347
Test: manual test
Change-Id: Iab09f13b2ff3d33e5c4d6a8710736307c26b17e7
1 file changed