spanification tool: preliminary cleanup.

Minor modifications:
- Add some comments and refactoring that improve my own understanding of
  the script.
- Remove the parts about "==== EDITS BEGIN ====", because it isn't used
  and I would like to ensure there no change appended, before exploring
  the tree.
- Add TODO about failed expectations.
- Run formatting, following Google coding style (4 spaces indentations).

Bug: 356643982
Change-Id: Ic306c730fa80c102773bc56f7e259a0f2d7fbc9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5757573
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Ali Hijazi <ahijazi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1337787}