Draft: Integration of Knot Resolver Manager

This MR tries to integrate Knot Resolver Manager into kresd. Manager is currently not production ready and this MR should NOT be merged until it is.

These integrations tasks need to be done before merging:

• manager as a git submodule
• apkg srcpkg creates tarball with manager included
• apkg build creates packages including manager
• create automated tests for kresd with manager