update rsyslog log size conf (#15821)

Why I did it
For some devices whose log folder size is larger than 200M, for example, 256M, the LOG_FILE_ROTATE_SIZE_KB should be 16M. and
THRESHOLD_KB=$((USABLE_SPACE_KB - (NUM_LOGS_TO_ROTATE * LOG_FILE_ROTATE_SIZE_KB * 2)))
= $(( (VAR_LOG_SIZE_KB * 90 / 100) - RESERVED_SPACE_KB)) - (NUM_LOGS_TO_ROTATE * LOG_FILE_ROTATE_SIZE_KB * 2)))
= $(( (256M * 90 / 100) - 4096)) - (8 * 16M * 2)))
the result would be a negative value

Work item tracking
Microsoft ADO (number only):
24524827
How I did it
Add a case for 400M, if the log folder size is between 200M and 400M, set the log file size to 2M

How to verify it
Do cmd "sudo logrotate -f /etc/logrotate.conf" on DUT which val/log folder size is 256M, and check the syslog.

files/image_config/logrotate/rsyslog.j2

@@ -36,6 +36,8 @@
 {
 {% if var_log_kb <= 204800 %}
     size 1M
+{% elif var_log_kb <= 409600 %}
+    size 2M
 {% else %}
     size 16M
 {% endif %}
@@ -52,6 +54,8 @@
         # Adjust LOG_FILE_ROTATE_SIZE_KB to reflect the "size" parameter specified above, in kB
 {% if var_log_kb <= 204800 %}
         LOG_FILE_ROTATE_SIZE_KB=1024
+{% elif var_log_kb <= 409600 %}
+        LOG_FILE_ROTATE_SIZE_KB=2048
 {% else %}
         LOG_FILE_ROTATE_SIZE_KB=16384
 {% endif %}