Update how auto indentation is handled by `Editor::newline`, in the case
where auto-indentation is not `AutoIndentationMode::None`, so as to
extend the range of the edits being applied to the beginning of the
line, in case the line only contains the indentation whitespace or
there's only whitespace indentation before the cursor position

This ensures that newlines are not left with whitespace.

Closes #34316 

Release Notes:

- Fixed auto indent leaving trailing whitespace on blank indented lines
when creating new lines.⁠

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Co-authored-by: dino <dinojoaocosta@gmail.com>