Add WiFi Access point support

[mattiaswal]

• Refactor Wi-Fi model
• Add Access Point support (including multi SSID)
• Fix misc minor bugs

This fix #1082 by adding a scan mode which is a wifi interface with only a radio in the wifi container.

Description

Checklist

Tick relevant boxes, this PR is-a or has-a:

• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
• Refactoring (please detail in commit messages)
• Build related changes
• Documentation content changes
  • ChangeLog updated (for major changes)
• Other (please describe):

[mattiaswal]

Future improvements (not included in this PR):

• Check the hardware for supported modes and validate in the c-code (for example it is impossible to run 5ghz on a radio only supporting 2.4Ghz)
• Implement show interface wifi0 survey or something, to see how crouded the 2.4Ghz band is
• Implement auto for channel, when generating config, use the python script (wifi-channel-map.py) to automatic set the current best channel, with fallback to 6 or something for 2.4.
• Implement more settings in AP mode (This only implement bare minimum)
• Today generate primary SSID och generate BSS is two different function, these could most likely be one

[troglobit]

A couple of comments and suggestions.

Also, please run Coverity Scan on this branch. There's a lot of C changes and additions ...

[troglobit]

Future improvements (not included in this PR):

* Check the hardware for supported modes and validate in the c-code (for example it is impossible to run 5ghz on a radio only supporting 2.4Ghz)

* Implement `show interface wifi0 survey` or something, to see how crouded the 2.4Ghz band is

* Implement `auto` for channel, when generating config, use the python script (wifi-channel-map.py) to automatic set the current best channel, with fallback to 6 or something for 2.4.

* Implement more settings in AP mode (This only implement bare minimum)

* Today generate primary SSID och generate BSS is two different function, these could most likely be one

I suggest putting this in a separate issue, this is good stuff!

[troglobit]

Great work! 💯🔥

I think the only thing I missed was a little cute picture early in the docs that show how things work. It's a massive wall of text otherwise ... but that we can add later on.