Support tag and status filters for netbox_prefixes data source

[kyle-burnett]

This PR adds support for using tag and status values as filters for the existing netbox_prefixes data source.

This PR also suggests removing the requirement that the data source must return at least 1 prefix as a result, and instead allows it to support returning 0 results:

	if *res.GetPayload().Count == int64(0) {
		return errors.New("no result")
	}

There seems to be some inconsistency across the data sources in regards to this behavior - some data sources support returning 0 results, and others don't.

I'll defer to the maintainers on whether or not we can remove the above check, but IMO, the provider should not error out of a plan just because a particular data source might return 0 results (especially since the Netbox API itself support this).

If a user has a requirement that a data source must return results, then IMO they should implement logic locally to account for that rather than having the provider force the behavior.

[fbreckle]

We already had a discussion about zero-result data sources in #42.
The points there still stand and eventually we should establish a consistent standard. I created a stub at https://github.com/e-breuninger/terraform-provider-netbox/wiki/General-data-source-structure

For the time being, let's just embrace inconsistency and merge, since it seems to be a requirement you need!

[kyle-burnett]

Thanks @fbreckle! I had not seen that previous discussion so thanks for linking to it.

The latest word from Hashicorp that I can find on 0-result data sources is here - hashicorp/terraform#30291 (comment)