Cancel GATT Connections in Discovery Client

This change addresses an issue where
the device discovery search GATT client
fails to cancel direct GATT connections
when bonding is removed for a device.

This resulted in app_hold_link leakage and
prevented future connection attempts to the device.

The fix ensures that:

- Direct GATT connections are canceled when a device is removed.
- Explicit disconnection occurs upon
  failed connection attempts to release the associated app_hold_link.

Bug: 356168480
Bug: 336890664
Test: atest BluetoothInstrumenationTests BumbleBluetoothTests
Change-Id: I197a3262b22b7b449291622edb7d4ef4624a640c