feat: Implement sub-device management and discovery features

[meirlo]

Add gateway sub-device discovery and management

Summary

Adds support for Gree gateway devices that manage multiple sub-devices (e.g., multi-split systems). During discovery, gateways are automatically queried for their sub-devices, which are returned as regular DeviceInfo objects that can be individually controlled.

Changes

Protocol layer (network.py)

• Added subList command and response types
• Added create_sublist_message to request sub-device lists from gateways
• Added handle_sublist_response handler for sub-device list responses
• Improved response type resolution to handle packets with top-level t field (used by subList responses)

Cipher (cipher.py)

• Added cipher_type class attribute to CipherBase, CipherV1 ("v1"), and CipherV2 ("v2")
• Added CipherBase.create(cipher_type) factory method for creating ciphers by type string

Device (device.py)

• Added get_sub_devices() method to query a gateway for its sub-devices
• bind() now auto-uses gateway_key and gateway_cipher from DeviceInfo when no explicit key is provided, enabling seamless sub-device binding
• update_state() now properly awaits the state response using an event, preventing race conditions
• Hardened current_temperature and version detection against non-numeric property values

Discovery (discovery.py)

• scan() now automatically queries discovered gateways for their sub-devices
• Added include_gateways parameter to optionally include gateway devices in results (default: False)
• Gateways are identified by sub_count > 0 from the subCnt field in scan responses

Device info (deviceinfo.py)

• Added sub_count, gateway_key, and gateway_cipher fields

Bug fixes

• Fixed test_mismatch_temrec_farenheit: send.side_effect was set to None instead of the fake handler
• Fixed test_issue_69: wraps=fake_send() was calling the function immediately instead of passing it as a callback

Tests

Added tests covering:

• Sub-device list request/response at the protocol level
• get_sub_devices() success and timeout paths
• Sub-device binding with explicit and gateway-inherited keys
• Sub-device state updates
• Discovery with subCnt parsing, gateway querying, and include_gateways flag

[meirlo]

this should close Add support for multiple units that connect with a single wifi controller

[codecov]

Codecov Report

❌ Patch coverage is 99.13793% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.84%. Comparing base (cff93f8) to head (0b4bfe7).

Files with missing lines	Patch %	Lines
greeclimate/device.py	98.07%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #148      +/-   ##
==========================================
+ Coverage   95.65%   96.84%   +1.18%     
==========================================
  Files           8        8              
  Lines         760      855      +95     
==========================================
+ Hits          727      828     +101     
+ Misses         33       27       -6     

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