Fix DataFrame.to_string() justification (2)
- [x] closes #16839, 
closes #13032
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

'Competes' with #22437 which attempts to revert `% d` to `%d` as suggested here: https://github.com/pandas-dev/pandas/issues/13032#issue-151973347 That turned out to affect a lot of tests, which in hindsight is expected; the `% d` has been around since at least 2012 (106fe994cb0eb2701).

Instead, this PR reverts parts of #11942 and embraces the leading space even when `index=False`. `df.to_string(index=False)` will print the leading space when the first column is positive only, as well as preserve leading/trailing spaces on first/last lines.

With the following code:
```python
import pandas as pd
def wrap_to_string(df, **kwargs):
    s = df.to_string(**kwargs)
    print(str(kwargs).center(25, '-'))
    for i, line in enumerate(s.split('\n')):
        print(f'^{line}$-{i}')
    print()
df = pd.DataFrame({'w': [1, 2], 'x': [3, -4], 'y': [555, 666],
                   'z': [777, -888], 'a': ['AAA', '   ']})
cols_ = list(map(list, ['wxyza', 'xyzaw', 'yzawx', 'zawxy', 'awxyz']))
for cols in cols_:
    wrap_to_string(df[cols], index=False)
```
Output with master:

```python
-----{'index': False}----  # last cell (three spaces) disappeared
^w  x    y    z    a$-0
^1  3  555  777  AAA$-1
^2 -4  666 -888$-2

-----{'index': False}----  # misaligned
^x    y    z    a  w$-0
^3  555  777  AAA  1$-1
^-4  666 -888       2$-2

-----{'index': False}----  # misaligned
^y    z    a  w  x$-0
^555  777  AAA  1  3$-1
^666 -888       2 -4$-2

-----{'index': False}----  # misaligned
^z    a  w  x    y$-0
^777  AAA  1  3  555$-1
^-888       2 -4  666$-2

-----{'index': False}----  # misaligned
^a  w  x    y    z$-0
^AAA  1  3  555  777$-1
^     2 -4  666 -888$-2
```

Output with this PR:

```python
-----{'index': False}----
^ w  x    y    z    a$-0
^ 1  3  555  777  AAA$-1
^ 2 -4  666 -888     $-2

-----{'index': False}----
^ x    y    z    a  w$-0
^ 3  555  777  AAA  1$-1
^-4  666 -888       2$-2

-----{'index': False}----
^   y    z    a  w  x$-0
^ 555  777  AAA  1  3$-1
^ 666 -888       2 -4$-2

-----{'index': False}----
^   z    a  w  x    y$-0
^ 777  AAA  1  3  555$-1
^-888       2 -4  666$-2

-----{'index': False}----
^   a  w  x    y    z$-0
^ AAA  1  3  555  777$-1
^      2 -4  666 -888$-2
```

Similar effect on Series as well.
