Change counterintuitive implementation of “Fastest IP address“ in case of non-A/AAAA response types

**Current behavior:**
The switch “Fastest IP address“ makes AdGuard query all configured upstreams. Then…

- if the upstreams return an A or AAAA record type, then AdGuard measures the time to open up a TCP connection to ports 80 and 443 of all returned IP addresses of all configured upstreams. AdGuard then return a manipulated DNS record, that only contains the fastest IP address.
- else (i.e. the upstreams return a different record type) AdGuard enters the normal “load-balancing“ mode. (see https://github.com/AdguardTeam/dnsproxy/blob/a87a3dfd6b737144a16ef92d130319d12184f129/proxy/exchange.go#L28 )

**Suggested behavior:**
If the upstreams return a different record type than A or AAAA, then AdGuard enters the normal “Parallel requests“ mode, i.e. change line 28 to “return upstream.ExchangeParallel(ups, req)“ (like in https://github.com/AdguardTeam/dnsproxy/blob/a87a3dfd6b737144a16ef92d130319d12184f129/proxy/exchange.go#L22 ).

**Rationale:**
As a user of “Fastest IP address“ I have to accept that generally all upstreams are queried in order to get the best overall system performance. In the case of A/AAAA records that is the fastest content server (not the fastest DNS answer). In case of other record types, that would be the fastest DNS answer, in my opinion.