PackedChararacteristicProxyAdapter doesn't seem to work for descriptors with new GATT adapter classes

To access descriptors I have been using code like this:

```
await characteristic.discover_descriptors()
if descriptors := characteristic.get_descriptor(ESS_MEASUREMENT_DESCRIPTOR):
self.valueDescriptor = PackedCharacteristicAdapter(descriptors, pack_format="0.0.208) I replaced PackedCharacteristicAdapter by PackedCharacteristicProxyAdapter. However, this fails like this:

```
File "/home/nnn/envi-ble/envi_ble/ess_service.py", line 133, in discover
valueDescriptor = PackedCharacteristicProxyAdapter(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/nnn/envi-ble/.venv/lib/python3.11/site-packages/bumble/gatt_adapters.py", line 172, in __init__
super().__init__(characteristic_proxy)
File "/home/nnn/envi-ble/.venv/lib/python3.11/site-packages/bumble/gatt_adapters.py", line 72, in __init__
characteristic_proxy.uuid,
^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'DescriptorProxy' object has no attribute 'uuid'
```