Config actions have standardized on camel case for a better developer experience

Config actions have standardized on camel case for a better developer experience to get away from mixed-case methods.

The simple_config_update config action has been renamed to simpleConfigUpdate.

The ensure_exists config action has been renamed to createIfNotExists to better describe what it does, creating config if it is not found.

Drupal core's recipes have been updated to use these new names. Contributed recipes will need to be updated.