meson build system

• Closes #350 (closed) (build system)
• Closes #212 (closed) (static build)
• Closes #279 (closed) (module namespace)
• Closes #290 (closed) (remove go modules support)
• Closes #338 (closed) (same vars for make / make install)
• Closes #451 (closed) (shadow lua global by func param)

Remaining TODOs

• fix CI tests
• update scripts for OBS to build successfully
• make sure OSX build works
• create migration documentation
• document/resolve missing parts (coverage)
• update respdiff toolchain
• document modules' lua dependencies

Review

• tarball includes the same files (see https://gitlab.labs.nic.cz/knot/knot-resolver/merge_requests/771#note_99606)
• CFLAGS, LDFLAGS for dev build hasn't changed unintentionally
• git diff doesn't contain forgotten TODO
• no commit contains DROP, WIP or TODO in title/message
• the same test suite is executed in CI
• check every module loads when installed (incl. dnstap)
• distro packages
  • no files were unintentionally removed
    • arch
    • deb
    • rpm
  • builds in OBS pass package test on a clean system
  • installed files/dir didn't unintentionally change permissions / owner
    • arch
    • deb
    • rpm
  • debian/ubuntu systemd works as before (service restart during update etc.)

Pre-merge

• [respdiff] - merge respdiff!50 (merged), update test infrastructure