This adds a %ToName runtime entry that uses the previously introduced
Object::ToName, which is based on the new Object::ToPrimitive method.
Also removes the need to expose ToName in various way via the builtins
and/or context.

Drive-by-fix: Let %HasProperty do the ToName conversion implicitly as
required.

BUG=v8:4307
LOG=n

Review URL: https://codereview.chromium.org/1319133002

Cr-Commit-Position: refs/heads/master@{#30435}