mesh: Introduce LPN-specific adv transmit properties
mesh: Introduce LPN-specific adv transmit properties

When the node is in LPN node, the LPN-Friend messages has its own
retries, so doing this on the advertising level (i.e. following the
network transmit state) is sub-optimal.

X-Original-Commit: 69ff4e282c308b6d182a4b67dee5ef97db27672d

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble