chore: update backends docs

[leoparente]

This pull request includes several documentation updates and a modification to the Dockerfile for the agent project. The most important changes include adding new sections and details to multiple backend documentation files and updating the Dockerfile to include additional capabilities for nmap.

Dockerfile Update:

• agent/docker/Dockerfile: Added libcap2-bin package and set capabilities for nmap to allow raw socket operations.

Documentation Updates:

Device Discovery Backend:

• docs/backends/device_discovery.md: Added a new section detailing the use of Diode entities and expanded the defaults section with more configuration options. [1] [2] [3]

Network Discovery Backend:

• docs/backends/network_discovery.md: Added a new section on Diode entities and expanded the defaults section with additional configuration options for scanning. [1] [2] [3]

Worker Backend:

• docs/backends/worker.md: Added a new section on Diode entities and clarified the scope definition options. [1] [2]

[mfiedorowicz]

Looks good