Revert "[metrics] Add StatsdBackend"

This reverts commit 3d2b93e6acb4e7ac6fc808f17813975f250dbf89.

Reason for revert: Breaks ART tests in chroot environment, as the
  libstatssocket library is not found. The error message is:

  CANNOT LINK EXECUTABLE
  "/apex/com.android.art/bin/art/x86/art_libdexfile_tests":
  library "libstatssocket.so" not found: needed by
  /apex/com.android.art/lib/libartd.so in namespace com_android_art

  How to reproduce in AOSP (e.g. on cuttlefish):

  $ lunch aosp_cf_x86_64_phone-userdebug && m && launch_cvd

  In another terminal, run art gtests on the device:

  $ unset ART_TEST_ANDROID_ROOT
  $ unset CUSTOM_TARGET_LINKER
  $ unset ART_TEST_ANDROID_RUNTIME_ROOT
  $ unset ART_TEST_ANDROID_TZDATA_ROOT
  $
  $ export ART_TEST_CHROOT=/data/local/art-test-chroot
  $ export OVERRIDE_TARGET_FLATTEN_APEX=true
  $ export ANDROID_SERIAL="0.0.0.0:6520"
  $
  $ . ./build/envsetup.sh
  $ lunch aosp_cf_x86_64_phone-userdebug
  $
  $ art/tools/buildbot-build.sh --target -j72
  $ art/tools/buildbot-cleanup-device.sh
  $ art/tools/buildbot-setup-device.sh
  $ art/tools/buildbot-sync.sh
  $
  $ export ISA=x86_64
  $ art/tools/run-gtests.sh -j8

Bug: 178236337
Test: art gtests in chroot env on aosp_cf_x86_64_phone-userdebug
Change-Id: Icbd38792f4d8828c40a53f037cefeebd777172bf
10 files changed