APIv4 - Simplify permissions

Overview

This simplifies the code to declare permissions in APIv4.

Before

Boilerplate was looking up a core api permission setting that doesn't exist, then overriding it.

After

No need for the extra lookup, just return the permission.

Comments

This also switches to "access CiviCRM" for "meta" actions (e.g. getFields). This is standard for every entity.