Increase PikeZ varlog size (sonic-net#13550)

Why I did it
To address error sometimes seen when running sonic-mgmt test_stress_routes.py::test_announce_withdraw_route on 720DT-48S

How I did it
Update boot0 logic to set platform specific varlog size for 720DT-48S

How to verify it
Verified that /var/log size increased and error is no longer observed when running test

files/Aboot/boot0.j2

@@ -469,8 +469,7 @@ write_platform_specific_cmdline() {
     local platform="$(cmdline_get platform)"
     local sid="$(cmdline_get sid | sed 's/Ssd$//')"
 
-    # set varlog size to 100MB
-    local varlog_size=100
+    local varlog_size=0
 
     # sonic_mode is set to fixed by default.
     sonic_mode="fixed"
@@ -544,6 +543,7 @@ write_platform_specific_cmdline() {
     fi
     if in_array "$sid" "PikeIslandZ" "PikeIslandZ-F" "PikeIslandZ-2F" "PikeIslandZ-R" "PikeIslandZ-2R"; then
         aboot_machine=arista_720dt_48s
+        varlog_size=2048
     fi
     if [ "$sid" = "BlackhawkT4O" ]; then
         aboot_machine=arista_7050px4_32s
@@ -640,18 +640,20 @@ write_platform_specific_cmdline() {
         read_system_eeprom
     fi
 
-    if [ $flash_size -ge 28000 ]; then
-        varlog_size=4096
-    elif [ $flash_size -gt 4000 ]; then
-        varlog_size=400
-    else
-        varlog_size=256
-        cmdline_add logs_inram=on
-        if [ $flash_size -le 2000 ]; then
-            # enable docker_inram for switches with less than 2G of flash
-            varlog_size=128
-            cmdline_add docker_inram=on
-        fi
+    if [ $varlog_size -eq 0 ]; then
+       if [ $flash_size -ge 28000 ]; then
+           varlog_size=4096
+       elif [ $flash_size -gt 4000 ]; then
+           varlog_size=400
+       else
+           varlog_size=256
+           cmdline_add logs_inram=on
+           if [ $flash_size -le 2000 ]; then
+               # enable docker_inram for switches with less than 2G of flash
+               varlog_size=128
+               cmdline_add docker_inram=on
+           fi
+       fi
     fi
 
     cmdline_add "varlog_size=$varlog_size"