Use the new config_target property in the datastore settings form

[jastraat]

This is a demonstration of the new way of tying configuration properties directly to form elements as of Drupal 10.2. This won't be backwards compatible to versions before Drupal 10.2.

fixes [org/repo/issue#]

• Test coverage exists
• Documentation exists

QA Steps

• Change the settings on admin/dkan/resources and save
• Export configuration and confirm that the changes are reflected in the exported configuration.

[jastraat]

@paul-m I mostly wanted to use this PR to remind myself of some of the Drupalcon config validation talk and demonstrate the changes in a concrete way; I know DKAN isn't ready yet to drop 10.1. (Although it does lose security support REALLY soon!)