Add proxy_config component

This CL moves proxy_config_dictionary and proxy_prefs to
src/components/proxy_config so that they can be used in
src/chromeos/network/onc for ONC translation.

BUG=470445
TBR=various for moving include files

Review URL: https://codereview.chromium.org/1221033002

Cr-Commit-Position: refs/heads/master@{#337257}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index f82b78a..68d319b8 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -129,6 +129,7 @@
     "//components/password_manager/core/browser",
     "//components/password_manager/core/common",
     "//components/policy:policy_component",
+    "//components/proxy_config",
     "//components/query_parser",
     "//components/rappor",
     "//components/renderer_context_menu",