Spun off Autofill PERF tests on its own package...

...so bugs on it (like starving the UI Thread) don't impact other tests

Test: mmma -j ./frameworks/base/apct-tests/perftests/autofill/ && \
  adb install -r $OUT/data/app/AutofillPerfTests/AutofillPerfTests.apk && \
  adb shell am instrument -w -e class android.view.autofill.LoginTest \
  com.android.perftests.autofill/android.support.test.runner.AndroidJUnitRunner

Bug: 38345816

Change-Id: I76346f1d1c45790788400fcd9765f6b424d99f4c