Spanification tool improvement

When rewriting C-style arrays to std::arrays, we sometimes need to add
extra braces around the initializer_list. This was handled by including
the entire intializer_list in the replacement text and which led to the
need to escape special characters in the replacement.

This change introduces the `additional_replacement` field used to split
some nodes into two. Splitting some replacements into two allows to
combine multiple changes without causing a replacement overlap. Indeed,
being able to submit two changes instead of one would avoid replacing a
large content of text shared by multiple changes.

For instance:
*(iterator++)
needs to two changes:
*(base::postIncrementSpan(iterator))
and then
base::postIncrementSpan(iterator)[0]

Using the `additional_replacement`, this change splits C-style array
rewrite nodes into two nodes where necessary. This removes the need to
escape initializer_list characters.

The first node contains the replacement directive for the array type and
the opening extra brace '{' (if any), the second node (marked as
dependent on the first) contains the trailing closing brace '}' (if
any).

Change-Id: Ib0addca44e4bcdb367e422cf50a2a3ca2dba0d09
Bug: 356643982
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6177729
Commit-Queue: Ali Hijazi <ahijazi@chromium.org>
Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1409603}