refactor: Use SpanReader over DataStream

This refactor does not change behavior. However, it avoids a vector
copy, which can lead to a minimal speed-up of 1%-5%, depending on the
call-site. This is mostly relevant for the fuzz tests and utils that
read large blobs of data (like a full block).

src/net.cpp

@@ -201,7 +201,7 @@ static std::vector<CAddress> ConvertSeeds(const std::vector<uint8_t> &vSeedsIn)
     const auto one_week{7 * 24h};
     std::vector<CAddress> vSeedsOut;
     FastRandomContext rng;
-    ParamsStream s{DataStream{vSeedsIn}, CAddress::V2_NETWORK};
+    ParamsStream s{SpanReader{vSeedsIn}, CAddress::V2_NETWORK};
     while (!s.empty()) {
         CService endpoint;
         s >> endpoint;