Use NetworkLinkService instead of Moat for the internet test

Spun out from #42605 (comment 3128884).

Instead of contacting Moat to test the internet, which would require user permission as per our design docs, we can use the nsINetworkLinkService API for:

1. Testing the internet connection in TorConnect.
2. Showing the internet connection state in about:preferences#connection.

As a result, we can also drop the "Test" button from about:preferences#connection and just make it a live status.

I'm guessing Android doesn't have an existing "Test" button anywhere.

Looping in UX for them to be aware, but this shouldn't need any input if it goes smoothly.

/cc @pierov @donuts @felicia

added 14.5 stable Desktop Next labels

assigned to @henry

marked this issue as related to #42605

marked this issue as related to #43185

removed Next label

added Doing label

mentioned in merge request !1371 (merged)

marked this issue as related to tor-browser-build#41348 (closed)

closed

removed the relation with tor-browser-build#41348 (closed)

marked this issue as related to tor-browser-build#41347 (closed)

mentioned in issue #41062 (closed)

mentioned in issue tpo/ux/team#114

marked this issue as related to tpo/web/manual#182 (closed)

mentioned in merge request tpo/web/manual!126 (merged)