More robust trailing expressions newline implementation

[Blacksmoke16]

Follow up to #15305 to handle another edge case I noticed.

Before this PR if you had a macro expression whose body is an Expressions node, and the last node of those expressions was a Block or If statement, the end keyword would be on the wrong line. For example

{%
  to_process = [] of Nil

  to_process.each do
    b = 2
    a = 1
  end
%}

would be stringified as:

{%
  to_process = [] of Nil

  to_process.each do
    b = 2
    a = 1 end
%}

This PR resolves this and adds more test coverage on similar cases.

Supersedes #15613