PowerDNS: Delete records before creating or modifying records

Add the number of changes and zone name to "making changes"

Fix windows filename problems

Force the value passed to FQDN to be a str

Modify Azure DNS Client logic to lazy load

Co-authored-by: Ross McFarland <ross@github.com>

Lazy loading the Azure DNS client ensures that the necessary network calls only occur when it is time to actually do something with the client.

Improve checking for and creating Azure DNS Zones

This change improves the process for checking for AzureDNS zones by using the known set and not relying upon custom error handling.

Since the provider already fetches the zones, octodns doesn't need to make a second call to check for the existence of the zone - _populate_zones already does that for us.

Rename extention zonefile test to avoid existing unit.tests.

Azuredns txt record too long , Skip alias entires

ZoneFileSource: allow users to specify file extension