Default to zero hop advert when booting + STEALTH_MODE flag

[jbrazio]

This pull request updates the advertisement sending logic in the mesh examples to allow for both "flood" and "zero hop" advertisement modes. The changes introduce a new flood parameter to the sendSelfAdvertisement method, making it possible to specify the advertisement type. The initial advertisement sent during setup in all examples is now a zero hop advertisement.

The CLI command "advert" continues to use flood advertisements for backward compatibility, as the flood parameter is omitted (defaulting to true).

Adds a STEALTH_MODE switch to remove automatic node advertisement when booting and DISCOVER_REQ processing.

[fdlamotte]

This behavior has already been discussed (and the fact that bootlooping repeaters are an issue)

Another change that should be included upon @ripplebiz decision ...

[jbrazio]

tbh I would prefer for repeaters not to issue any adverts during setup().. nevertheless I kept it backward compatible but having less impact on the network by using zh.

[mattzzw]

This would fix the DDOS/advert situation, see issue #1091

[jbrazio]

Implements #1217 (comment)

  -D MIN_LOCAL_ADVERT_INTERVAL=60
  -D MAX_LOCAL_ADVERT_INTERVAL=240
  -D MIN_FLOOD_ADVERT_INTERVAL=3
  -D MAX_FLOOD_ADVERT_INTERVAL=48

[mattzzw]

Why is local in minutes and flood in hours?

[jbrazio]

Why is local in minutes and flood in hours?

@ripplebiz