Add dependency for python 3.8, reenable sdist

[timkpaine]

This PR does three things:

• fix missing runtime dependency for python 3.8
• skip profiling test code if graphviz package missing (xref Skip graphviz tests if not installed locally #30)
• reenable sdist tests on full builds

"Full" build: https://github.com/Point72/csp/actions/runs/7855760939

[timkpaine]

I'm going to make ldclassic a cmake flag since it looks like the cmake function to detect it doesn't work, then I'm going to try another full build with Mac enabled and then we can merge.

[ngoldbaum]

LGTM

I got a request from @robambalu to add Python3.8 wheels to the build so I'm going to do add that in a followup. Let me know if that steps on anything you were planning.

[ngoldbaum]

I'm seeing this when I try to merge, which I think is incorrect?

Closing and re-opening to check if that will let me merge this on github, otherwise I'll merge it manually.

[ngoldbaum]

Maybe someone turned on branch protection and required signed commits sometime in the last few days?

[ngoldbaum]

I guess so:

git push upstream main
Total 0 (delta 0), reused 0 (delta 0), pack-reused 0
remote: error: GH006: Protected branch update failed for refs/heads/main.
remote: error: Commits must have verified signatures. Required status check "test (ubuntu-22.04, 3.11, false)" is expected.
To github.com:Point72/csp.git
 ! [remote rejected] main -> main (protected branch hook declined)
error: failed to push some refs to 'github.com:Point72/csp.git'