debian: update debhelper compat Level before 9 are deprecated says debhelper 12. Upgrade to 10, which is available in Debian oldstable and old Ubuntu releases to be conservative (and since we probably don't need more).

extend-diff-ignore = "^(contrib/|.gitlab-ci.yml|.hg-format-source|MANIFEST|Makefile|docs/tutorial/.netlify|hgext3rd/evolve/hack/|tests/.testtimes)"