Regression: "Out of host memory" on Nvidia ICD

- 1593a67b7f2a97e26d4f88fb70bf711e7682a395 (just before the #189) is known good
- 167ae7c6ee7c96118ed7308e3b9e74a8d199088f is broken

Here's a log of the CI failure: https://gitlab.tiker.net/inducer/arraycontext/-/jobs/462367

Host memory grows to 6-ish gigabytes when running this by hand and then keels over. If run with `--sw`, this fails as before, but it succeeds upon resuming when rerun. I suspect there's a memory leak here somewhere.

@matthiasdiener Could you take a look?

Compare commits 1593a67b7f2a97e26d4f88fb70bf711e7682a395 and 167ae7c6ee7c96118ed7308e3b9e74a8d199088f, with attention to the changes around #189. Reproduce the CI failure from job 462367 and compare normal execution with --sw. Done means identifying the regression and confirming that the Nvidia ICD run no longer exhausts host memory.

Written by the indexing model from the issue text.