Update self-hosted runners (linux.12xlarge.ephemeral) to newer OS

[bryantbiggs]

Based on failures like https://github.com/pytorch/builder/actions/runs/8300660718/job/22725657004 from #1734, it looks like the self-hosted runners might be using Centos7, or another older OS, that has an older version of glibc. If the runners are using Centos7, and EOL for that is coming up in June 2024, we should look at updating the runners to a newer OS (i.e. Centos8)

xref actions/runner#2906

cc @atalman since I believe only Meta employees will be able to carry out this task

in addition, #1734 was primarily created due to EOL versions being used (Ubuntu 18.04 and NodeJS 16) - so all of this is really just to unblock getting off OS and runtime versions that are long passed end of support