Bug 40009: Change the default search engines

Closes #40009 (closed).

It seems android-components uses the previous xml format for search engines. So, I took these from Tor Browser 60, but tried do as least changes as possible to the already existing ones in android-components. One exception is DDG, where I kept the POST url that is used in desktop, although I'm not exactly sure if we actually need that, or we could switch go GET.

Then, I took the list.json from current 78, but I removed all the locale-specific parts of it, as this seems to be working correctly. My idea is to keep the search engines locale-independent without having to change this list when we support new locales. This may increase rebase conflicts, but I think fixing these should be relatively easy: just remove the contents of "regionOverrides" and "locales" again.

The engines are displayed in alphabetical order because Fenix is sorting them this way, so I'll do a patch there for this.

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