[ProfileShowcase] Add network preferences support for accounts

[alexjba]

Description

The purpose of this task is to provide the backend support for network preferences in the showcase accounts. The network preferences could be part of the showcase save API and needs to be part of showcase for a contact models.

When changing the network preferences from wallet settings the profile showcase should be updated.

TBD: the network preferences format

This task will provide the status-go implementation and the nim integration for save action (possibly update as well when the account settings is changed) and to extend the nim showcase accounts model for a contact to provide the network preferences.

Design

          Here we discussed we may need the **network preferences** too. Not sure which was the final decisions here @alexjba ?

Originally posted by @noeliaSD in https://github.com/status-im/status-desktop/pull/13998#discussion_r1542906129