* Extend container image name validator
The current validator allows certain invalid names (e.g. upper
case), but disallows valid cases (such as ttl.sh/myimage).
Improve the container image validator to support more valid
options and at the same time disallow some of the invalid
options.
Note that this is not a complete/perfect validation still. A much
much more sophisticated regex would be necessary to be 100% accurate.
Also we format the string and replace {machine}/{arch} using Python
format strings. In that regard the image format in Supervisor deviates
from the Docker/OCI container image name format.
* Use an actual invalid image name in config validation
* Improvements to DNS validator to include IPv6 (#1312)
* improvements to DNS validator to include IPv6
* fixed the DNS validators
* updated per suggestions
* Update const.py
* Update dns.py
* Update validate.py
* Update validate.py
* Update dns.py
* Update test_validate.py
* Update validate.py
* Cleanup
* Don't set default DNS server as default
* Remove update local resolver
* Fix lint
