Issue #2192259 by andypost, amateescu, damiankloip: Remove ConfigField.. Item and List classes + interfaces.

Issue #2152825 by plopesc, swentel, Berdir: Rename FieldItemBase::getFieldSetting[s]() to getSetting[s]().

Issue #2143797 by agentrickard, amateescu: GetDefaultValue() fails with ConfigurableEntityReferenceFieldItemList.

Issue #2090541 by plopesc, yched: Avoid storing numeric target_id()'s for default values in field instance CMI files.