Remove ProxyResolver from update_engine

Current ProxyResolver code only supports no-proxy. Therefore it is
barely any use. Remove current implementation for a better one.

Test: th
Bug: 235816007
Change-Id: Ieb46dedf6c6ea86b11c81d7691c2adb578d3d97d
diff --git a/common/multi_range_http_fetcher.h b/common/multi_range_http_fetcher.h
index ef32f0d..849ed32 100644
--- a/common/multi_range_http_fetcher.h
+++ b/common/multi_range_http_fetcher.h
@@ -46,7 +46,7 @@
  public:
   // Takes ownership of the passed in fetcher.
   explicit MultiRangeHttpFetcher(HttpFetcher* base_fetcher)
-      : HttpFetcher(base_fetcher->proxy_resolver()),
+      : HttpFetcher(),
         base_fetcher_(base_fetcher),
         base_fetcher_active_(false),
         pending_transfer_ended_(false),
@@ -101,7 +101,8 @@
   }
   // TODO(deymo): Determine if this method should be virtual in HttpFetcher so
   // this call is sent to the base_fetcher_.
-  virtual void SetProxies(const std::deque<std::string>& proxies) {
+  void SetProxies(const std::deque<std::string>& proxies) override {
+    HttpFetcher::SetProxies(proxies);
     base_fetcher_->SetProxies(proxies);
   }