Add support for high bit depth multichannel images

[aclark4life]

We now have two approaches for this:

• Add support for high bit depth multichannel images #8224
• Image -> Arrow support #8330

Discuss 🍿

[aclark4life]

If I understand correctly, the difference between the two:

• Update PIL's C data structure to accommodate high bit depth multi channel images.
• Add Arrow's C data structure library to Pillow to accommodate high bit depth multi channel images.

With the former, we have the potential for making pointer math mistakes but avoid including Arrow's C library in Pillow. With the latter we have a more robust data structure for the low price of including Arrow's C library.

[wiredfool]

That's not really correct --- My arrow support here doesn't do anything to enable high bit depth images. All it does is use the lightest weight arrow integration (headers/structs only) to export the existing pillow image memory blocks as arrow using the arrow_c_arrayinterface, which is the spiritual successor to thearray_interface`. There are a few caveats, in that the data has to be packed, so there are formats that won't work (anything with row padding/alignment), and it currently doesn't support multi block images (>16mb by default).

I'd like to fix those, and get the reverse working -- read arrow array as an image.