Fix a false negative for Layout/ExtraSpacing

[koic]

This PR fixes a false negative for Layout/ExtraSpacing when some character are vertically aligned.

For example, there is a wasted space before the do keyword.

d_is_vertically_aligned  do
  _______________________d
end

The d char is accidentally vertically aligned and cannot be detected:

$ bundle exec rubocop --only Layout/ExtraSpacing
(snip)

1 file inspected, no offenses detected

Looking at the test code, it looks like this is to allow vertical alignment of dots in method calls:

y, m = (year * 12 + (mon - 1) + n).divmod(12)
m,   = (m + 1)                    .divmod(1)

https://github.com/rubocop/rubocop/blob/v1.54.1/spec/rubocop/cop/layout/extra_spacing_spec.rb#L172-L177

Therefore, this PR tweaks the alignment logic to be closer to the expected behavior.

And it also suppresses the following new offenses found with this tweak:

$ bundle exec rubocop
(snip)

lib/rubocop/string_interpreter.rb:37:18: C: [Correctable] Layout/ExtraSpacing: Unnecessary spacing detected.
        when /\d/       then interpret_octal(escape)
                 ^^^^^^
spec/rubocop/target_finder_spec.rb:74:35: C: [Correctable] Layout/ExtraSpacing: Unnecessary spacing detected.
    create_file('dir1/executable',  '#!/usr/bin/env ruby')
                                  ^

1513 files inspected, 3 offenses detected, 3 offenses autocorrectable

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[bbatsov]

Looks good. Thanks!