Remove libcurl support from update_engine_sideload.

While sideloading an update from recovery we don't need nor want to
download payload from HTTP(S) URLs, only local file:// are supported.
This patch moves libcurl_http_fetcher and certificate_checker files out
of libpayload_consumer dropping the libcurl and libssl dependencies from
it and the update_engine_sideload.

Bug: 27178350
TEST=build UE for Brillo and Android. Unittests still pass and
update_engine_sideload doesn't link to libcurl.

(cherry picked from commit 14c0da88a93aa7b1aa71d5e7e923b537f0d419f3)

Change-Id: I6195fc0a8ceedfc7fd1a92bdd0acc55ace2c1232
diff --git a/real_system_state.h b/real_system_state.h
index 13fbfad..480b4b7 100644
--- a/real_system_state.h
+++ b/real_system_state.h
@@ -28,8 +28,8 @@
 #include <power_manager/dbus-proxies.h>
 #include <session_manager/dbus-proxies.h>
 
+#include "update_engine/certificate_checker.h"
 #include "update_engine/common/boot_control_interface.h"
-#include "update_engine/common/certificate_checker.h"
 #include "update_engine/common/clock.h"
 #include "update_engine/common/hardware_interface.h"
 #include "update_engine/common/prefs.h"