This CL will temporarily regress memory since we will store the name
both on the SFI and the ScopInfo. Future CLs will do the following:
- Collapse the name field on SFI with the scopeInfo field
- Store the ScopeInfo on the Context instead of the closure so we
  don't strongly hold on to the closure unnecessary

Drive-by-fix:
 - Mark ScopeInfo accessors as const

Bug: v8:7066
Change-Id: I7ef47d858352bb0bb76ad105f194eabce06938ed
Reviewed-on: https://chromium-review.googlesource.com/939476Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51680}