[CI] slangpy testing not checking proper backend

[skallweitNV]

It looks like the slangpy testing doesn't actually update the slang compiler in the slangpy package before running tests, so essentially it runs tests with a very old version of slang (the version shipped with slangpy). I did update to latest slang locally and a lot of slangpy tests were failing (which was easy to fix fortunately) but the fact that the slangpy tests in slang's CI did pass got me worried.

[aasgaonkar]

looking into this

[aasgaonkar]

is this the expected failure from slangpy 0.30 - https://github.com/shader-slang/slang/actions/runs/15432749878/job/43433440047 ?

[aasgaonkar]

we have the fix ready: #7334
it is failing CI as expected; we are awaiting a slangpy package update to fix CI bug, then we can merge this fix.