Update to 1.7.0 and rework metaprogramming

[rasen68]

• Add PyRpc and PyRegistry to lib.rs wrapping device::RpcDescriptor and device::RpcRegistry and exposing helpful methods
• Add _rpc_list() and _rpc_registry() to PyDevice to return device::RpcList.vec and PyRegistry
• Use PyRpc to not have to parse raw metadata in __init__.py
• Consolidate Device._get_obj_*() metaprogramming methods into cleaner _RpcSurvey _Rpc, _SamplesDict, and _SamplesList classes
• _Rpc subclasses for types of call methods
• Use PyRegistry to recursively instantiate RPCs, fixing bug where an RPC would override its children if added after.
• Add brief docstrings, type hinting, and __repr__s