[dhcp_server] Add dhcpservd to dhcp_server container (#16560)

Why I did it
Part implementation of dhcp_server. HLD: sonic-net/SONiC#1282.
Add dhcpservd to dhcp_server container.

How I did it
Add installing required pkg (psutil) in Dockerfile.
Add copying required file to container in Dockerfile (kea-dhcp related and dhcpservd related)
Add critical_process and supervisor config.
Add support for generating kea config (only in dhcpservd.py) and updating lease table (in dhcpservd.py and lease_update.sh)

How to verify it
Build image with setting INCLUDE_DHCP_SERVER to y and enabled dhcp_server feature after installed image, container start as expected.
Enter container and found that all processes defined in supervisor configuration running as expected.
Kill processes defined in critical_processes, container exist.

dockers/docker-dhcp-server/docker_init.sh

@@ -1,5 +1,21 @@
 #!/usr/bin/env bash
 
+
+# Generate supervisord config file
+mkdir -p /etc/supervisor/conf.d/
+# Generate kea folder
+mkdir -p /etc/kea/
+udp_server_ip=$(ip -j -4 addr list lo scope host | jq -r -M '.[0].addr_info[0].local')
+hostname=$(hostname)
+# Generate the following files from templates:
+# port-to-alias name map
+sonic-cfggen -d -t /usr/share/sonic/templates/rsyslog.conf.j2 \
+    -a "{\"udp_server_ip\": \"$udp_server_ip\", \"hostname\": \"$hostname\"}" \
+    > /etc/rsyslog.conf
+sonic-cfggen -d -t /usr/share/sonic/templates/port-name-alias-map.txt.j2,/tmp/port-name-alias-map.txt
+
+# Make the script that waits for all interfaces to come up executable
+chmod +x /etc/kea/lease_update.sh /usr/bin/start.sh
 # The docker container should start this script as PID 1, so now that supervisord is
 # properly configured, we exec /usr/local/bin/supervisord so that it runs as PID 1 for the
 # duration of the container's lifetime