Scan network interfaces once at startup

[OlivierHecart]

Network interfaces scanning is a costly operation.
It was previously done at each link creation which leaded to significant CPU consumption at startup when lot of links were established.
Network interfaces scanning is now performed once at startup. The result of this initial scan is then used for the whole life of the process.

[github-actions]

PR missing one of the required labels: {'bug', 'new feature', 'breaking-change', 'documentation', 'dependencies', 'enhancement', 'internal'}

[sashacmc]

Shouldn't this be made configurable?
For example, in the case of VPN or something similar, interfaces can appear and disappear.
Some interfaces may not be there at the start, but will appear later, if the user wants to take this case into account, then such optimization can harm him.