refactor(rust): extract network code to agama-network

[imobachgs]

Problem

While working on the agama monitor command, I needed to use the Event enum, which is defined in agama-server, from agama-lib. agama-lib is a dependency of agama-server, so I decided to move the Event to agama-lib. However, it depends on some network stuff which is defined in agama-server. So I had to move more stuff to agama-lib.

Let's put aside the fact that we need to improve the Event enum (turning it into a composition of smaller events).

Solution

To improve the code organization, I have added a new agama-network package which the business logic for the network area resides now. It is a big change, but it brings some benefits:

• Better code organization: most of the network code is in a single place.
• In the future, if we follow this approach with other areas, the build time should improve.

Additionally, the agama-utils package contains OpenAPI and D-Bus utilities but, in the future, it could even contain the BaseHTTPClient and other reusable code.

Future work

• The settings module should live in agama-lib, as it can be considered kind of an interface to the network settings.
• Consider whether the types module still makes sense.

Testing

• Tested manually