Handle properly stringifying single line blocks

[Blacksmoke16]

Depends on, and is similar to, #15305 but for Block nodes.

Previously code like:

{%
  [1, 2, 3].each { |v| pp v }
  [1, 2, 3].each do |v|
    pp v
  end
%}

Would always stringify single-line blocks as a do/end block:

{% [1, 2, 3].each do |v|
  pp(v)
end
[1, 2, 3].each do |v|
  pp(v)
end
 %}

But now, in-conjunction with the other PR, results in:

{%
  [1, 2, 3].each { |v| pp(v) }
  [1, 2, 3].each do |v|
    pp(v)
  end
%}

I threw a bunch of test cases at it with the assumption the code may not have had the formatter ran on it and all seems 👍.

Marking as draft and skipping CI. Will rebase/trigger CI once the other dependent PR is merged. But wanted to get this opened for feedback.