Previously, all ThisExpression's had kNoSourcePositions leading to
incorrect error messages like this:

  ➜ d8 -e "function t() { for (const x of this) {} } t();"
  unnamed:1: TypeError: undefined is not a function
  function t() { for (const x of this) {} } t();
            ^
  TypeError: undefined is not a function
      at t (unnamed:1:11)
      at unnamed:1:43


This patch allows creation of a ThisExpression with a source position,
leading to a better error message:

  ➜ d8  -e "function t() { for (const x of this) {} } t();"
  unnamed:1: TypeError: this is not iterable
  function t() { for (const x of this) {} } t();
                                 ^
  TypeError: this is not iterable
      at t (unnamed:1:32)
      at unnamed:1:43


This patch does not remove the existing cached version of
ThisExpression and instead creates a new one when required.

Bug: v8:6513
Change-Id: Idee4fe8946a9b821d06ff4a5e7eaefe54874ec59
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2345226Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Sathya Gunasekaran  <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69300}