espressif: report GATT ATT errors as specific exceptions

[dhalbert]

• Follow-up to espressif: fix GATT client read/write completion and timeouts #11512

Code by Claude, reviewed by @dhalbert.

Problems

• GATT client reads and writes reported ATT errors from the peer as "Unknown system firmware error: 261" and the like, instead of SecurityError or another specific exception.
• check_nimble_error() called unknown NimBLE return codes "system firmware" errors.
• Unknown error codes were printed in decimal, so they could not be looked up in NimBLE's documentation.

Changes

• bleio_gattc_read() and bleio_gattc_write() pass ATT error statuses to check_ble_error(), which now maps the common ones:

ATT error	Exception
0x02 Read Not Permitted	BluetoothError: read not permitted
0x03 Write Not Permitted	BluetoothError: write not permitted
0x05 Insufficient Authentication	SecurityError: Insufficient authentication
0x08 Insufficient Authorization	SecurityError: Insufficient authorization
0x0C Insufficient Encryption Key Size, 0x0F Insufficient Encryption	SecurityError: Insufficient encryption
0x0D Invalid Attribute Value Length	ValueError: Invalid length
any other	BluetoothError: Unknown gatt error: 0x01xx (nordic's existing message)

• Unknown errors from check_nimble_error() and check_ble_error() both print "Unknown BLE error: 0x%04x". NimBLE's return-code documentation lists codes in that form, e.g. 0x0213 for HCI error 0x13.

Testing

Metro ESP32-S3 as central, Feather nRF52840 on nordic 11.0.0-alpha.1 as peripheral:

Operation	Result
Read a NO_ACCESS characteristic	BluetoothError: read not permitted
Write a NO_ACCESS characteristic	BluetoothError: write not permitted
Read an ENCRYPT_NO_MITM characteristic without pairing	SecurityError: Insufficient authentication
Write 8 bytes to a 4-byte fixed_length characteristic	ValueError: Invalid length
Ordinary read and write	unchanged

0x08, 0x0C and other ATT errors could not be produced with a CircuitPython peripheral.

Not changed

• connect() to an absent device usually returns a Connection that is not connected instead of raising. That will be a separate PR.