Refactor code

[danischm]

Breaking change: refactor resource keys:

• Use keys derived from identifying fields in all resources
  instead of only resources that are referred to by other resources.
  This way, inserting a resource in the middle of the list
  does not cause existing resources to be modified/recreated.
• Add ${domain.name}/ to all keys.
• Consistently use format() for keys instead of string interpolation.

Breaking change: replace net_switch_stacks_routing_interfaces_dhcp_{first,not_first} with a single net_switch_stacks_routing_interfaces_dhcp resource.

Apply default values consistently:

• Apply defaults everywhere - many resources and nested fields did not have them applied.
• Change defaults paths to always be rooted at domains. instead of having different roots for domain/organization/network resources.
• Fix outdated paths to defaults: make the path the same as for the value (skipping arrays).
• Map values from the YAML (and apply defaults) in one place - directly in the local variable, instead of doing part of that in the resource as well.
  • Convert empty array fields to null in the variable directly.
  • Remove the catch-all data field and map all nested values explicitly - this is necessary to apply defaults everywhere.
• Remove redundant if try(...) after loops that result in empty arrays by default anyway.

Fix a lot of fields where schema differences were missed previously.

[vozhyk-]

Adding some things I noticed when fixing this to pass the tests.