Migrate to HPy 0.9.0.

[fangerer]

I've rebased Du Toit's original branch onto branch hpy-9.2.0 of this repo (not sure who created that branch initially).
Then I've migrated to HPy 0.9.0 and this is the corresponding PR.

The tests are not passing but haven't been passing before (making them pass is a separate task).
This is the current test output on my box:

Running selftest:
**********************************************************************
File "/Users/fa/work/repos/pyhandle/pillow-hpy/selftest.py", line 57, in __main__.testimage
Failed example:
    type(im.im) # doctest: +ELLIPSIS
Expected:
    <... '...ImagingCore'>
Got:
    <class 'ImagingCoreOriginal'>
**********************************************************************
File "/Users/fa/work/repos/pyhandle/pillow-hpy/selftest.py", line 78, in __main__.testimage
Failed example:
    im.getextrema()
Exception raised:
    Traceback (most recent call last):
      File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/doctest.py", line 1350, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest __main__.testimage[24]>", line 1, in <module>
        im.getextrema()
      File "/private/var/folders/pn/n5d8qrwj6_z9_jm37l2s245r0000gn/T/venv-ujson_hpy/lib/python3.10/site-packages/PIL/Image.py", line 1342, in getextrema
        extrema.append(self.im.getband(i).getextrema())
    ValueError: band index out of range
**********************************************************************
File "/Users/fa/work/repos/pyhandle/pillow-hpy/selftest.py", line 111, in __main__.testimage
Failed example:
    im.getextrema()
Exception raised:
    Traceback (most recent call last):
      File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/doctest.py", line 1350, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest __main__.testimage[41]>", line 1, in <module>
        im.getextrema()
      File "/private/var/folders/pn/n5d8qrwj6_z9_jm37l2s245r0000gn/T/venv-ujson_hpy/lib/python3.10/site-packages/PIL/Image.py", line 1342, in getextrema
        extrema.append(self.im.getband(i).getextrema())
    ValueError: band index out of range
**********************************************************************
1 items had failures:
   3 of  59 in __main__.testimage
***Test Failed*** 3 failures.
*** 3 tests of 59 failed.
make: *** [install] Error 1

[DuToitSpies]

Looks good to me, thanks for making the changes!

[DuToitSpies]

I think this comment can go - there was an issue while benchmarking in which PyPy didn't like HPy_BuildValue, but it worked fine on CPython and GraalPy, so these HPy_BuildValue comments are just a legacy of then

[DuToitSpies]

I remember I had an issue here where casting image to Imaging worked, but using ImagingObject_AsStruct didn't compile. If this compiles, it's fine