Each context type get own instance type:
- we can make CSA checks more strict in couple places,
- it is requires step for advanced evaluation without side effects.

R=yangguo@chromium.org

Bug: v8:7588
Change-Id: I585e8b55a280a909fc3c6069ed30e34b7040d0c7
Reviewed-on: https://chromium-review.googlesource.com/977041
Commit-Queue: Aleksey Kozyatinskiy <kozyatinskiy@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52191}