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/setup-ssh.sh

@@ -0,0 +1,15 @@
+#!/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
+# Setup sshd
+sed -i 's/^PasswordAuthentication yes//' /etc/ssh/sshd_config
+sed -i 's/^#\(PasswordAuthentication\) yes/\1 no/' /etc/ssh/sshd_config
+sed -i 's/^#\(PermitRootLogin\) .*/\1 no/' /etc/ssh/sshd_config
+systemctl restart sshd