Improve routine-update's handling of `debputy` packages and `debhelper-compat` 14 packages
This MR covers multiple things:
- Use
dh_assistantto read the compat level to partially supportX-DH-Compat(read-only, cannot update it). Since write is not supported, I would not see https://bugs.debian.org/1091921 as closed by this MR (but a step closer to it). - Check for
Build-Driverfield to determine if a compat level is "mandatory". - Remove assumption that
debian/rulesexist. The file will not exist withBuild-Driver: debputy.
Note there is not a changelog since that would cause a merge conflict with !16 (merged).