PY-9778 Do not warn about unused inner functions with unknown decorators

I added helper class PyKnownDecoratorUtil that contains list of
well-known decorators from Python's standard library and redefined
several existing methods from PyUtil in terms of this class.
(cherry picked from commit 031ab39)
Merge remote-tracking branch 'origin/139' into 139
Removed tests that have been wrongly cherry-picked from master without the corresponding fix
Fixed WEB-2405 Code style / HTML / "Do not indent children ... or if tag size more than" actually works like "more or equals"
(cherry picked from commit 613f745)