What does this implement/fix? Explain your changes.

This PR fixes certain connections missing nodes when the before or after where args are empty.

Issue stems from the fact that get_nodes() in several connection resolvers simply checked for isset( $this->args['{before|after'}]) before slicing the array.

Along those lines, I also got rid of the unnecessary isset() checks in a couple of places.

to test:

Run the following query and confirm withOffset and withoutOffset are the same:

{
  withOffset: taxonomies(first:2, before:""){
    nodes{
      name
    }
  }
  withoutOffset: taxonomies(first:2){
    nodes{
      name
    }
  }
}

taxonomies should be replaced with the other relevant connection types: contentTypes, registeredScripts, registeredStylesheets, plugins, taxonomies, themes, and roles.

Any relevant logs, error output, GraphiQL screenshots, etc?

Without PR (v1.7.2)

With PR:

Where has this been tested?

Operating System: Ubuntu 20.04 (wsl2) + Devilbox + PHP v8.0.15

WordPress Version: v5.9.1