CNR Provider: Review CI / Docs / Capabilities (add NAPTR, SSHFP)

[KaiSchwarz-cnic]

@tlimoncelli I went through all the capabilities and played around with the CentralNic Reseller API. All this is now updated and great that I've been able to identify SSHFP and NAPTR as supported record types.
Finally, I went through the Dev Guide for new Provider Modules and reviewed the missing parts.

• Reviewed Provider Capabilities
• Added support for NAPTR record
• Added support for SSHFP record
• reviewed documentation
  • cleanup requested providers
  • added CNR to the provider list
• reviewed reported linting issues (golangci-lint)
• fixed go releaser regexp

Integration Tests passed:

...
--- PASS: TestDualProviders (4.89s)
=== RUN   TestNameserverDots
No nameservers found
=== RUN   TestNameserverDots/No_trailing_dot_in_nameserver
--- PASS: TestNameserverDots (0.12s)
    --- PASS: TestNameserverDots/No_trailing_dot_in_nameserver (0.00s)
PASS
ok      github.com/StackExchange/dnscontrol/v4/integrationTest  381.239s

[tlimoncelli]

Please rebase

[tlimoncelli]

(It looks like the only file that has a merge conflict is generated. A quick go generate ./... should (?) fix it.)

[tlimoncelli]

Sorry for all the emails. I was trying to construct a "suggested change" that would enable the merge, but I forgot that wouldn't work due to permissions issues.