Misc: lifemngr-daemon-on-UOS

For cross-VM S5 notify via vUART, life_mngr service is running on UOS.
It is listening on /dev/ttyS1 to get SOS's commands.
The protocol is: SOS send "shutdown", UOS feedback "acked".

When SOS triggle shutdown, SOS can 1) check VM's status until UOS
stopped, 2) retry shutdown UOS normally with timeout.
So, no matter life_mngr server is running, SOS's shutdown procedure will
properly finish.

Tracked-On: #3564
Signed-off-by: fuyanX <yanx.fu@intel.com>
Acked-by: Yan, Like <like.yan@intel.com>

misc/life_mngr/life_mngr.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=ACRN lifemngr daemon
+After=systemd-resolved.service
+
+[Service]
+Type=simple
+ExecStart=/usr/bin/life_mngr uos /dev/ttyS1
+StandardOutput=journal
+StandardError=journal
+Restart=yes
+
+[Install]
+WantedBy=multi-user.target