feat: OBS-439 - diode-sdk-python: ingester wrappers

[mfiedorowicz]

Add wrappers for ingester entity classes generated from protobuf with a main goal to flatten nested types for users convenience.

• [x] unit tests
• [x] usage examples in README

[linear[bot]]

OBS-439 diode-sdk-python: simplify/flatten ingestion input

I.e. instead of ```python Device( name="Router 1", device_type=DeviceType( model="ISR4321", manufacturer=Manufacturer(name="Cisco"), ), site=Site(name="Site 1"), ) ``` We could have ``` Device( name="Router 1", device_type="ISR4321", manufacturer="Cisco", site="Site 1", ) ```