This is is a preparatory CL to detach the JSFunction from the Context.
We mainly rewrite the DebugScopeInterator to no longer rely on the a
JSFunction to be around. Additionally the empty_function needs to have
a proper ScopeInfo now.

Drive-by-fix: Improve ScopeInfo debug printing

Bug: v8:7066
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I2f2fa0e78914a12e076384e0e1234c2322ad1ee8
Reviewed-on: https://chromium-review.googlesource.com/918721
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52791}