This changes the behavior of overload resolution to not consider if the
call happens in a branching context (i.e., with implicit True and False
labels from a conditional operator or statement).
That way, it is not possible to get different behavior accidentially
by using an operator in the wrong context. Instead, there will be a
compile error because the call happened in a non-branching context, or
because it is ambiguous without this information.

The test doesn't perfectly fit the issue (impossible until we have
negative tests), but instead tests that equality on HeapNumber's works
in boolean contexts, which is something Peter fixed already in
https://crrev.com/c/1432596.


Bug: v8:8737 v8:7793
Change-Id: I08a3801891587aac705dc93b1c65b0c6cf164107
Reviewed-on: https://chromium-review.googlesource.com/c/1456093Reviewed-by: Peter Wong <peter.wm.wong@gmail.com>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59625}