wheels: get 'tileiras' from system install, not 'cuda-toolkit' wheels

[jameslamb]

Follow-up to #2548

Contributes to rapidsai/build-planning#324

• switches to wheel builds and pip devcontainers getting tileiras from the system-installed CTK, not cuda-toolkit wheels.

Notes for Reviewers

Benefits of the tileiras change

• one less version to need to remember to update when we bump the CTK version we build against
• consistent with how we get NVCC from the system install, not wheels
• removes a source of patching in DLFW builds (where a system CTK is always preferred to one provided by wheels)

How I tested this

relied on CI

[jameslamb]

I'm going to admin-merge this, in the interest of reducing how much stuff is in flight for 26.10.

It's highly unlikely that these changes could have affected the conda C++ tests, and I don't want to wait another 3.5 hours for them to get merged.