Allow setting default tags on resources managed by the provider

[mraerino]

This implements something similar to what the AWS provider offers: https://registry.terraform.io/providers/hashicorp/aws/latest/docs#default_tags-1

The idea is to have the ability to add some tags to all resources. This is handy for stuff like marking resources managed through terraform, e.g.

provider "netbox" {
  default_tags = ["terraform-managed"]
}

[mraerino]

sorry, the move to providerState is quite a large refactor. do you want me to break this into smaller pieces somehow or is it fine like this?

[mraerino]

@fbreckle anything against landing this?

[fbreckle]

Nope, I had a look at it already. Very nice feature indeed!

I did not see a test for the functionality itself, i.e. configure provider with default tags, create a - I don't know - netbox_region or something without dependencies and check if it has the tags. Did I miss it?

[mraerino]

Very good call on the testing. Uncovered some bugs which lead to some refactoring. Should be good now