Gnocchi: archive policy rules support

[ozerovandrei]

It would be great if this repo supported API for Gnocchi archive policy rules.

Documentation reference: archive-policy-rule.

• List archive policy rules
• Get an archive policy rule
• Create an archive policy rule
• Update an archive policy rules
• Delete an archive policy rules

[pierreprinetti]

Please open an issue in the Gophercloud repository in case it's still relevant