Fixup scripts to set up a new CI node (#9348)

* Clean up node setup scripts for new CI boxes

* Move files under ci directory

* Set CUDA env var to setup cuda drivers

* Fixup and add README

* shellcheck

* Apply review feedback, rename dir and setup files

Co-authored-by: publish-docs.sh <maintainers@solana.com>

ci/setup-new-buildkite-agent/set-hostname.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+HERE="$(dirname "$0")"
+
+# shellcheck source=ci/setup-new-buildkite-agent/utils.sh
+source "$HERE"/utils.sh
+
+ensure_env || exit 1
+
+set -xe
+
+echo "preserve_hostname: false" > /etc/cloud/cloud.cfg.d/99-disable-preserve-hostname.cfg
+systemctl restart cloud-init
+hostnamectl set-hostname "$1"