[gpu] Exercise installer with all supported GPU types (#1302)

* [gpu] Exercise installer with all supported GPU types

* enabling GPU agent by default
* for cuda repo, add known signing keys to trustdb
* move variable definition to prepare function
* add some TODO notes for installing this script as a custom image
* spark supports maximum 1 GPU per executor
* printing warning when old cuda is used with ubuntu22
* built a list of PCI devices for each supported GPU type
* improvements to disk usage metrics display

* Exercised script with variety of images

* Supported on 2.0.27-debian10
* * added fallback to using gsutil when gcloud sdk < 402
* * adoptium, cran-r and gcloud pgp databases updated
* * writing multi-valued gpg databases using `gpg --import --no-default-keyring --keyring ...` vice `gpg --dearmor -o`
* * evaluating variable name for keyring path when writing sources.list file
* driver builds for P4, P100, and V100 now tested
* * build driver from proprietary source when PCI Device ID < 0x1E00 (Turing)
* * separating open vs non-free kmod builds into their own gcs path
* renamed completion variable for nvidia container toolkit from nvtk to nvctk
* removed export of METADATA_HTTP_PROXY variable, since it's only used in this one function