Type declaration may contain a parent type in an "extends" clause.
This CL changes the token type of the name after such a clause
from std::string to Identifier*. The resulting SourcePosition is then
used to implement the "goto-definition" link from that name to the
definition of the parent type.

R=mvstanton@chromium.org

Bug: v8:8880
Change-Id: I9ea6cd83e4d6ef535906e36626f64d458c7d0270
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1511481Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60179}