Only attach template exposed form region if is selected

Problem/Motivation

If we are using the display "Layout builder" at the view, the same template with regions is still used despite not using the "Exposed form region" plugin.

This breaks any other views that are using the "Layout Builder" display.

Steps to reproduce

Create a view that uses "Exposed Form Region" and it takes "views-view--layout-builder--efr.html.twig" template.
Create a view that NOT use "Exposed Form Region", and it ALSO takes "views-view--layout-builder--efr.html.twig" template.

Proposed resolution

Limit the template #theme attribute only if current exposed form plugin is "exposed_form_region" plugin Id.

Also minimal fixes about little warnings.