work around pillow 10.0.0 changes

[CPBridge]

Fix for #243 :

• Require pillow >=10.0.0
• Update highdicom.color to use the new organisation of constants found in pillow==10.0.0

[CPBridge]

ok so it appears that pillow 10.0.0 does not support python 3.7. This is going to be mmore complex that I had thought. We will have to either drop support for 3.7 or put some hacks in place that can deal with both pillow<10.0.0 and pillow>=10.0.0. I am reluctant to drop support for 3.7 personally, as it is still in widespread use

[CPBridge]

OK so this is ugly but I added logic that works around the breaking change at pillow 10.0.0 so that we can continue to support python 3.7. While this doesn't smell great, in my opinion, it is worth it to avoid dropping an entire version of python just to avoid this tiny little API change. I note that over the last 6 months around 5-10% of our users are using 3.7: https://pypistats.org/packages/highdicom. What do you think @hackermd ?