Rename resource_hints.config to resource_hints.settings

Problem/Motivation

While not a strict requirement by any means, generally speaking modules use module.settings for maintaining configuration settings. Resource Hints currently uses resource_hints.config.

Proposed resolution

While it's not necessarily a problem, for consistency purposes I recommend switching it to resource_hints.settings instead.

This involves renaming config/install/resource_hints.config.yml to config/install/resource_hints.settings.yml and updating all instances of resource_hints.config to resource_hints.settings anywhere it exists in the rest of codebase.

This is technically a breaking issue if someone already has the module installed, but given that we're still in alpha now is the time to get this change in.