refactor(sessionresolver): adapt to changing network conditions (#238)

* feat(sessionresolver): try many and use what works

* fix(sessionresolver): make sure we can use quic

* fix: the config struct is unnecessary

* fix: make kvstore optional

* feat: write simple integration test

* feat: start adding tests

* feat: continue writing tests

* fix(sessionresolver): add more unit tests

* fix(sessionresolver): finish adding tests

* refactor(sessionresolver): changes after code review

internal/engine/session.go

@@ -109,7 +109,11 @@ func NewSession(config SessionConfig) (*Session, error) {
 		BogonIsError: true,
 		Logger:       sess.logger,
 	}
-	sess.resolver = sessionresolver.New(httpConfig)
+	sess.resolver = &sessionresolver.Resolver{
+		ByteCounter: sess.byteCounter,
+		KVStore:     config.KVStore,
+		Logger:      sess.logger,
+	}
 	httpConfig.FullResolver = sess.resolver
 	httpConfig.ProxyURL = config.ProxyURL // no need to proxy the resolver
 	sess.httpDefaultTransport = netx.NewHTTPTransport(httpConfig)