[fuchsia] Create an entry-point script to run driver tests on Fuchsia (#48359)

* [fuchsia] Create an entry-point script to run driver tests on Fuchsia

This script currently only paves the device. This will soon run a
driver test on a NUC in LUCI.

* reference the engine script and fix comment

dev/bots/run_fuchsia_tests.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+# Copyright 2014 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This script has been adapted from:
+# https://github.com/flutter/engine/blob/master/testing/fuchsia/run_tests.sh
+# Any modifications made to this file might be applicable there as well.
+
+# This expects the device to be in zedboot mode, with a zedboot that is
+# is compatible with the Fuchsia system image provided.
+#
+# The first and only parameter should be the path to the Fuchsia system image
+# tarball, e.g. `./run_fuchsia_tests.sh generic-x64.tgz`.
+#
+# This script expects `pm`, `dev_finder`, and `fuchsia_ctl` to all be in the
+# same directory as the script.
+
+set -Ee
+
+# The nodes are named blah-blah--four-word-fuchsia-id
+device_name=${SWARMING_BOT_ID#*--}
+
+if [ -z "$device_name" ]
+then
+  echo "No device found. Aborting."
+  exit 1
+else
+  echo "Connecting to device $device_name"
+fi
+
+reboot() {
+  # note: this will set an exit code of 255, which we can ignore.
+  ./fuchsia_ctl -d $device_name ssh -c "dm reboot-recovery" || true
+}
+
+trap reboot EXIT
+
+./fuchsia_ctl -d $device_name pave  -i $1