feat(client/cordova/apple): [1980] randomize list of dns severs

[serge-r]

Just add a simple shuffle for list of dns servers

According to issue https://github.com/Jigsaw-Code/outline-apps/issues/1980

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[serge-r]

fixed tests

[SanchesS]

@fortuna sorry for disturbing you, but this fix also will help our app with millions of users — a lot of them use Outpost VPN and this VPN by default use only 1.1.1.1 DNS server and we see using our client metrics that sometimes a small ratio of DNS requests is throttled (and then failed) by 1.1.1.1 and our users facing issues within our app

We investigated a lot into this issue (we spend a weeks into it) and DNS server rotation (not only 1.1.1.1) will definitely improve network stability requests for people using Outline VPN as their main VPN service