refactor: #3577050: Generalize field widget action dispatch in the base class.

Move aiAutomatorsAjax and the submit-phase runAutomatorSubmit handler into AutomatorBaseAction so every FWA subclass does not have to redeclare them. Introduce two extension points plugins override only when their widget diverges from the per-delta default:

• setFormInput() writes the widget-specific shape into $form_state->getUserInput() during the submit phase.
• transformFormInput() adapts a single field item to the widget's user-input shape; the default returns $item->toArray().

Add two helpers used by the dispatch:

• updateItemsCount() pushes the new delta count into field widget state before rebuild so multi-value widgets (e.g. cshs) scaffold enough sub-elements to render every automator-produced delta — the core fix for the referenced child issue #3578660.
• widgetHandlesMultipleValues() detects widgets declaring multiple_values=TRUE so plugins supporting several widget types (ClassificationOptionsSelect) can branch on shape.

Closes #3577050