APIv4 - Standardize generic entity name resolution so that classNames do not have...

APIv4 - Standardize generic entity name resolution so that classNames do not have to equal entityNames

This will allow the addition of a CiviCase API which cannot have the className "Case" because that is a reserved php keyword

Also cleans up other entities that use `static::class` in place of entityName because it's not a good pattern to replicate.