FunctionBlueprint holds a SharedFunctionInfo, FeedbackVector and a
Hints object that represents what we know about the Context of
the "function-to-be." Since we occasionally synthesize a
FunctionBlueprint object from a JSFunction (when we have it),
it can happen that sometimes the Context hint is a concrete
Context object, and other times it's a VirtualContext, representing
a context created sometime during the bytecode execution of the
function under optimization. Moreover, both such FunctionBlueprints
can exist in the same run due to the vagaries of CALL_IC feedback
(ie, sometimes you have a JSFunction, other times you don't).

More details in doc:
https://docs.google.com/document/d/1F1FxoDzlaYP5l5T6ZcZacV3LCUp5elcez05KWj-Mp78/edit?usp=sharing

Bug: crbug:1024282
Change-Id: Id4055531333b3dcbdb93afd23d9a226728292e11
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1926151
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65127}