Create trait for Config Filters

Problem/Motivation

The \Drupal\config_filter\Config\FilteredStorage expects an array of \Drupal\config_filter\Config\StorageFilterInterface but there is only a base class for plugins. Filters do not need to be plugins though.

Proposed resolution

Add a trait that filters can use for methods that they don't need to override.

Remaining tasks

User interface changes

none

API changes

new trait which base class can use

Data model changes

none