Copy profiles over from apparmor-profiles/ubuntu/20.04/

I propose we get rid of the apparmor-profiles repo and the apparmor-profiles-extra package. Both are redundant in light of the existing extras area in this repo (and /usr/share/apparmor/extra-profiles/ in the apparmor-profiles package), the package ships only a fraction of the profiles in the repo, and the repo has gone neglected for months. IMO, there's ample reason to put it out of its misery.

This MR has four commits:

1. Fix the check-parser and check-extras targets so they don't break with an abstractions/ directory under profiles/extras/;
2. Copy over all the useful profiles/abstractions from ubuntu/20.04/ (note that there is no newer directory present) without any modifications;
3. Give each profile a proper profile keyword;
4. Update the include directives to current conventions.

This should cover everything we want to retain file-wise, though you may want to diff the ubuntu-browsers abstractions just to be sure nothing of value is lost. The outstanding issues/MRs should ideally be followed up on, even if it's just asking the reporter to re-file them here, before the repo is archived.