[hostcfgd] Delay hostcfgd and aaastatsd for faster boot time (#7965)

#### Why I did it
hostcfgd is starting at the same time as 'create_switch' method is called on orchagent process.
This introduce a degradation on the function execution time which eventually cause the fast-boot flow and a boot scenarion in general to run slower (~6 seconds).
This change will delay the start time of this daemon.
The aaastatsd will delay as well since it has a dependency on hostcfgd, so it is required to delay both.
90 seconds determined as the maximum allowed downtime for control plane to come back up on fast-boot flow.

#### How I did it
Add two timers for hostcfgd and aaastatsd  services in order to delay the startup of these services.

#### How to verify it
Install an image with this change and observe the daemons start 90 seconds after the system boot.

src/sonic-host-services-data/debian/sonic-host-services-data.aaastatsd.service

@@ -12,6 +12,3 @@ Restart=on-failure
 RestartSec=10
 TimeoutStopSec=3
 
-[Install]
-WantedBy=sonic.target
-

src/sonic-host-services-data/debian/sonic-host-services-data.aaastatsd.timer

@@ -0,0 +1,11 @@
+[Unit]
+Description=Delays aaastatsd daemon until SONiC has started
+PartOf=aaastatsd.service
+
+[Timer]
+OnActiveSec=1min 30 sec
+Unit=aaastatsd.service
+
+[Install]
+WantedBy=timers.target sonic.target
+

src/sonic-host-services-data/debian/sonic-host-services-data.hostcfgd.service

@@ -9,6 +9,3 @@ After=sonic.target
 Type=simple
 ExecStart=/usr/local/bin/hostcfgd
 
-[Install]
-WantedBy=sonic.target
-

src/sonic-host-services-data/debian/sonic-host-services-data.hostcfgd.timer

@@ -0,0 +1,11 @@
+[Unit]
+Description=Delays hostcfgd daemon until SONiC has started
+PartOf=hostcfgd.service
+
+[Timer]
+OnActiveSec=1min 30 sec
+Unit=hostcfgd.service
+
+[Install]
+WantedBy=timers.target sonic.target
+