This change adds support for `const` redeclaration on REPL mode with
the semantincs recommended in the design doc:

1) REPL scripts should not be able to reassign bindings to `const`
   variables.

2) Re-declaring `const` variables of page scripts is not allowed in
   REPL scripts.

3) Re-declearing `const` variables is not allowed in the same REPL
   script.

4) `const` re-declaration is allowed across separate REPL scripts.

5) Old references to previously declared variables get updated with the
   new value, even those references from within optimized functions.

Design doc: https://goo.gle/devtools-const-repl

Bug: chromium:1076427
Change-Id: Ic73d2ae7fcfbfc1f5b58f61e0c3c69e9c4d85d77
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2865721Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Luis Fernando Pardo Sixtos <lpardosixtos@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#74510}