Merge branch 'opt-refactor' into 'zone-events-queue'

EDNS refactoring v2

Refactored the EDNS even more. The `edns_parameters` structure has been removed, only the OPT RR is used everywhere. Also removed any EDNS-related stuff from the packet functions, except for a getter, but there is one for TSIG as well, so it's not an issue probably. It's also possible to remove it, as it only saves a few characters of code.

Unittests pass, functional tests also.

Please review again.