[CI] Update Azure Pipelines distros and fix shebang

- Add devel targets for Docker and Remote stages
- Split existing targets into 2.21 stages
- Fix shebang in timing.py to pass sanity test
- Remove unnecessary shebang ignores from sanity ignore files

Signed-off-by: Hideki Saito <saito@fgrep.org>

tests/utils/shippable/timing.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env python
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type