Add Ability to export DNS filters after premium license is expired

### Prerequisites

### Problem Description

After Adguard premium license is expired, you can't access your previous DNS filters, blocklist, or allow list. This makes it impossible to export or retrieve your customizations

### Proposed Solution

Instead of completely preventing users without a premium license from accessing the DNS tab, allow users to view and explore the DNS tab.

In addition to allowing former premium users to export their filters and block/allowlists, this would allow prospective premium users to see the full functions of the DNS protection as well as create sample filters.

To enforce the paywall, just prevent the toggle button to enable DNS protection button from functioning or redirect users who click it to the paywall.

### Alternatives Considered

Another option would be an "Export Data" tab in the settings which would allow users to export all customizations from one location.

This option can allow users to select what specific data they want to export. The data can contain safari custom filters, DNS filters and other custom configuration data.

### Additional Information

In my opinion, implementing both options, the DNS tab access and the "Export Data" option would make the Adguard UX better however, the DNS tab access would be more important as it has the potential to attract new subscribers.