Record seperate virtual instance types for entries in FeedbackVectors:
- FEEDBACK_VECTOR_ENTRY_TYPE

 Bug: v8:7266

Change-Id: Ibea0615ecd23099e0107505e5d33cf194aade7c0
Reviewed-on: https://chromium-review.googlesource.com/866878
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50678}