[gnoland] Add nspkgs (namespace packages) ABCI query

[leohhhn]

Description

We should add a namespace endpoint to gnoland that will allow us to fetch packages & realms under a certain namespace. To prevent outputs that are too large, this endpoint should support pagination, and possibly alphabetical sorting and sorting by date added. The endpoint should also be capped to a certain number of results to prevent excessive stress on the node.

This RPC would be used to display available packages via gnoweb, such as for this link.

See comments below. We should implement this as an ABCI query with a pagination parameter.

cc @moul

[leohhhn]

Related: #2189

From the issue:

Published Packages:

• List {p,r}//** published packages.
• Implement a new RPC call with pagination to fetch this information.
• Ideally sorted by publication date.

[leohhhn]

@moul

A suggested approach for this from @zivkovicmilos's side was to create a new ABCI query for this. WDYT?