We currently have several ways to share symbols that are used in
both native scripts and the runtime. This change unifies this.
We do not use the symbols registry since we don't need the
registry any longer after bootstrapping, but the registry stays
alive afterwards.

R=mlippautz@chromium.org, rossberg@chromium.org

Review URL: https://codereview.chromium.org/1293493004

Cr-Commit-Position: refs/heads/master@{#30280}