Fix _theme hook caches are not invalidated when user visit page that has different theme.

In function varbase_layout_builder_theme() getActiveTheme condition is used.

When admin login, the active theme becomes the admin theme and theme function runs and output will be cached for all.

'blb_section' => [
        'template' => 'vlb-section',
        'render element' => 'content',
        'base hook' => 'layout',
      ],

However, these hooks/pages do not have an active theme cache context.

This causes, sometimes vlb-section template used sometimes blb-section template used depending on which active theme is used first.