udev: split wifi and bt rules into two separate files, add systemd unit file, and add BT mac retry

The udev rule for bluetooth doesn't work on systemd[1], by splitting the rule into two separate rules, distros can leave this bluetooth rule out when packaging for systemd.

Distros packaging bootmac will have to make note of the new rule files/names.

This also includes a systemd unit file that can be used to autostart bootmac when bluetooth stuff is starting up (e.g. when the adapter is available), and provides a nicer way to add delays instead of trying to delay udev scripts, scripts that take 'too long' for udev can cause problems.

1. https://github.com/systemd/systemd/issues/35003

bootmac-bluetooth.rules

-# 
+#
 # Configure the MAC addresses of the WLAN and Bluetooth interfaces when they appear.
 # Copyright (c) Dylan Van Assche (2022)
 # SPDX-License-Identifier: GPL-3.0-or-later
 #
 
-ACTION=="add", SUBSYSTEM=="net", KERNEL=="wlan0", RUN+="/usr/bin/bootmac"
-ACTION=="add", SUBSYSTEM=="bluetooth", KERNEL=="hci0", RUN+="/usr/bin/bootmac"
+ACTION=="add", SUBSYSTEM=="bluetooth", KERNEL=="hci0", RUN+="/usr/bin/bootmac --bluetooth"