GUI: gmodeler fix adding tool

[landam]

This PR fixes two regressions introduced recently.

Steps to reproduce

1. Open graphical modeler
2. Add some tool (tested on v.buffer)
3. Fill required params (in the case of v.buffer: input and output)
4. Press OK

Adding new tool fails with:

Traceback (most recent call last):
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gui_core/forms.py", line 828, in OnOK
    cmd = self.OnApply(event)
          ^^^^^^^^^^^^^^^^^^^
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gui_core/forms.py", line 841, in OnApply
    self.get_dcmd(
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/panels.py", line 507, in GetOptData
    data = dataClass(
           ^^^^^^^^^^
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/model.py", line 1380, in __init__
    self._defineShape(width, height, x, y)
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/model.py", line 1580, in _defineShape
    ogl.EllipseShape(self, width, height)
TypeError: EllipseShape.__init__() takes 3 positional arguments but 4 were given

This regression was introduced by 2cf98da.

After fixing this issue a new regression appears:

Traceback (most recent call last):
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gui_core/forms.py", line 828, in OnOK
    cmd = self.OnApply(event)
          ^^^^^^^^^^^^^^^^^^^
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gui_core/forms.py", line 841, in OnApply
    self.get_dcmd(
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/panels.py", line 536, in GetOptData
    data.Update()
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/model.py", line 1555, in Update
    self._setPen()
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/model.py", line 1538, in _setPen
    self.SetPen(self._getPen())
                ^^^^^^^^^^^^^^
  File "/home/martin/src/grass/dist.x86_64-pc-linux-gnu/gui/wxpython/gmodeler/model.py", line 1508, in _getPen
    if rel.GetTo().IsParameterized():
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'ModelDataSingle' object has no attribute 'IsParameterized'

This regression was introduced by f99780c.

This PR fixes both issues in the modeler. @echoix BTW, there are similar modifications (removed __init__ and kept self) in 2cf98da related to ColumnSorterMixin. I didn't checked it, but possibly it's introducing similar regression.

[echoix]

This mentions ColumnSorterMixin #4277

[echoix]

I see the subtle difference with the change in the model file.
It wasn't included in my PR initially, but ended up there after review:
#4045 (comment)

I still don't see the difference with the __init__ though... Unless that class ends up having a __call__ attribute.