[mle] remove and add the multicast addresses when mesh-local prefix changes (#2012)
[mle] remove and add the multicast addresses when mesh-local prefix changes (#2012)

This commit changes how the link-local and the realm-local all-thread
multicast addresses are maintained. A change in mesh-local prefix
triggers a re-calculation of multicast addresses. When such a change
happens the old addresses are first removed/unsubscribed from the
interface and then the new ones are subscribed to. This ensures that
`OT_CHANGED_IP6_MULTICAST_(UN)SUBSRCRIBED` flags are set properly and
host/user is informed of the change of the multicast addresses.
georgecpr/openthread,georgecpr/openthread,lanyuwen/openthread,fbsder/openthread,xiaom-GitHub/openthread,gandreello/openthread,xiaom-GitHub/openthread,gandreello/openthread,mszczodrak/openthread,erja-gp/openthread,vaas-krish/openthread,jwhui/openthread,turon/openthread,chshu/openthread,chshu/openthread,pvanhorn/openthread,fbsder/openthread,librasungirl/openthread,bukepo/openthread,aeliot/openthread,georgecpr/openthread,gandreello/openthread,lanyuwen/openthread,aeliot/openthread,vaas-krish/openthread,lanyuwen/openthread,srickardti/openthread,erja-gp/openthread,aeliot/openthread,aeliot/openthread,LeZhang2016/openthread,georgecpr/openthread,srickardti/openthread,bukepo/openthread,openthread/openthread,jwhui/openthread,xiaom-GitHub/openthread,vaas-krish/openthread,JakubBrachTieto/openthread,erja-gp/openthread,pvanhorn/openthread,LeZhang2016/openthread,jwhui/openthread,erja-gp/openthread,pvanhorn/openthread,bukepo/openthread,librasungirl/openthread,JakubBrachTieto/openthread,LeZhang2016/openthread,mszczodrak/openthread,JakubBrachTieto/openthread,JakubBrachTieto/openthread,lanyuwen/openthread,chshu/openthread,fbsder/openthread,LeZhang2016/openthread,abtink/openthread,gandreello/openthread,chshu/openthread,mszczodrak/openthread,openthread/openthread,pvanhorn/openthread,lanyuwen/openthread,openthread/openthread,turon/openthread,georgecpr/openthread,vaas-krish/openthread,lanyuwen/openthread,vaas-krish/openthread,LeZhang2016/openthread,gandreello/openthread,xiaom-GitHub/openthread,turon/openthread,pvanhorn/openthread,mszczodrak/openthread,gandreello/openthread,chshu/openthread,georgecpr/openthread,LeZhang2016/openthread,mszczodrak/openthread,srickardti/openthread,abtink/openthread,abtink/openthread,srickardti/openthread,mszczodrak/openthread,turon/openthread,bukepo/openthread,JakubBrachTieto/openthread,erja-gp/openthread,jwhui/openthread,vaas-krish/openthread,xiaom-GitHub/openthread,aeliot/openthread,aeliot/openthread,librasungirl/openthread,xiaom-GitHub/openthread,chshu/openthread,fbsder/openthread,openthread/openthread,erja-gp/openthread,abtink/openthread,JakubBrachTieto/openthread,librasungirl/openthread,fbsder/openthread,fbsder/openthread,pvanhorn/openthread