This patch introduces new scopes in the preparser, just like they
are introduced by the parser, in the following places:

-   blocks
-   try statement
-   switch statement
-   scoped statements, in several places
-   for statement
-   eager function bodies

R=rossberg@chromium.org
BUG=
LOG=N

Review URL: https://codereview.chromium.org/1906793002

Cr-Commit-Position: refs/heads/master@{#35708}