Add support for TLD check and allowing Cross-Origin iframes option

[varjolintu]

Adds support for checking Top-Level-Domains from hostnames, and returning a base domain. The implementation is almost similar to KeePassXC's keepassxreboot/keepassxc#9935 that is using a cookie API for TLD's (there's no direct API for it).

If a Cross-Origin iframe is detected, the popup will show a new option:

Pressing the button will add the tab/window URL to Site Preferences and enables the new "Allow Cross-Origin iframes" option.

Content script's isIframeAllowed() now performs the following:

• Checks if Cross-Origin iframes are allowed by Site Preferences.
• Checks the base domain of window/iframe using TLD list.
• Allows the iframe automatically if it's under the same base domain.
• Disallows iframes that do not match with the tab's/window's URL.

Unit tests are disabled for now, because it's unclear how the background script can be tested with Cookies API enabled. I ran the same tests directly in the background script when making the feature, and all of those passed.

Fixes #2076.

[varjolintu]

There are some problems with the automatic subdomain detection with Firefox. Trying to fix it.

EDIT: It's a problem with First-Party Isolation enabled. Seems there might be a bug in Firefox. So this feature will not work for e.g. Tor Browser automatically. User needs to make a manual exception.

[Felix-Official]

The same problem. How can I get the fixed version?

[varjolintu]

@Felix-Phi What do you mean?

[droidmonkey]

Works perfectly on the test/issue sites