[FL-2957] Unified Info API, App Error, Data Xchange

[gsurkov]

BEFORE MERGING

Make sure to merge this first and then update the flipperzero-protobuf submodule to point to the dev branch.

Changes

Library:

• new rpc_property_get() method
• new rpc_app_data_exchange_send() and rpc_app_data_exchange_recv() methods
• new rpc_app_get_error() method

FlipperCmd:

• Add GET-PROP command (Get property)
• Add GET-ERROR command (Get application-specific error)
• Add DATA-XCHANGE command (Exchange user data with application)
• Fix incorrect rpc_system_device_info() and rpc_system_power_info() behaviour