Fix pl_upgrades environment (numpy, cuda, gcc)

[vaclavhanzl]

Fix versions to make pl_upgrades usable again:

• avoid numpy 2
• use own cuda tools with proper explicit gcc version

Should fix #494 and #477 and likely few other issues (see below, the list seems long).

[jnwei]

Thanks for the fix Vaclav!

[vaclavhanzl]

Thanks for the merge Jennifer.