chore: resource pool support for PBS

[phillip-gaisford]

Description

Add some resource pool constants to describe PBS as the underlying workload manager on the HPC cluster, then update the WebUI to handle PBS.

Also, update unsupportedQPosSchedulers, as per Bradley.

Test Plan

Tested manually on the horizon & casablanca clusters, with Slurm & PBS.

Horizon (Slurm):

Commentary (optional)

Checklist

• Changes have been manually QA'd
• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.
• If modifying /webui/react/src/shared/ verify make -C webui/react test-shared passes.

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[stoksc]

lgtm though let me add someone from web

[keita-determined]

LGTM as a member from web