[UI] Do not include trailing EOL character when counting lines

- Adjust the counting of the number of lines of a file to match the
amount of rendered lines. This simply means that a file with the content
of `a\n` will be shown as having `1 line` rather than `2 lines`. This
matches with the amount of lines that are being rendered (the last empty
line is never rendered) and matches more with the expecation of the
user (a trailing EOL is a technical detail).
- In the case there's no EOL, the reason why it was counting
'incorrectly' was to show if there was a trailing EOL or not, but now
text is shown to tell the user this.
- Integration test added.
- Resolves Codeberg/Community#1612

options/locale/locale_en-US.ini

@@ -1331,6 +1331,8 @@ normal_view = Normal View
 line = line
 lines = lines
 from_comment = (comment)
+no_eol.text = No EOL
+no_eol.tooltip = This file doesn't contain a trailing end of line character.
 
 editor.add_file = Add file
 editor.new_file = New file