Only deprecate fromarray mode for changing data types

[radarhere]

Further discussion in #9018 has suggested that some of the functionality in the fromarray() mode argument is still useful.

#9018 (comment)

When this was proposed, there was the one legitimate use case mentioned (P), this is definitely another. Specifying that the uint8 pixels represent YCbCr instead of RGB is the sort of cast that is safe and useful for importing -- it's essentially the same operation as specifying a colorspace -- rather than specifying a bit layout which is what trips people up.

This PR restores it for changing

• L -> P
• LA -> La, PA
• RGB -> YCbCr, LAB, HSV
• RGBA -> RGBa, RGBX, CMYK

[djhoese]

Any idea when this might be merged? And any idea what version it might be released in?

The previous deprecation has been causing a lot of warnings in my projects which I think this PR should fix. Thanks for allowing these cases.

[radarhere]

Pillow 12.0.0 is scheduled for October 15. I expect that it will be merged by then.