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/disable-nouveau.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
+
+cat <<EOF > /etc/modprobe.d/blacklist-nouveau.conf
+blacklist nouveau
+options nouveau modeset=0
+EOF
+
+update-initramfs -u