Add dbg image for development/debugging purposes

[wiredfool]

Provides a new docker image ubuntu-22.04-jammy-amd64-valgrind-dbg with debug symbols, source, and enough tools to track down extension issues that show up on the valgrind image.

[hugovk]

We have some cache cleanup in the others to keep the layers/images smaller (re: #91):

docker-images/ubuntu-22.04-jammy-amd64-valgrind/Dockerfile

Line 34 in 4591bf5

&& apt-get clean && rm -rf /var/lib/apt/lists/*

[wiredfool]

I'm not as worried about size on this one, and there's much more of a possibility to need to inline add things to the image while working.

[radarhere]

I'm unsure if this is deliberate or not - this hasn't been added to GitHub Actions?

[wiredfool]

No, not in GHA -- This is an incremental build off of the other one, and essentially local development stuff that I don't want to lose and be able to reference elsewhere. I'm actually thinking that this is more useful to build locally than to have in the actual saved docker images. Though, I'm not sure if the build will work properly if we're not logged into dockerhub, so might need to tweak the makefile a bit there.

Other thought -- this should probably be included here: https://github.com/python-pillow/Pillow/blob/main/docs/reference/c_extension_debugging.rst and some of the setup to make GDB work with the python stack should be done as well.