[CRM] Add support for snat, dnat and ipmc crm resources (#6012)

Signed-off-by: Prabhu Sreenivasan prabhu.sreenivasan@broadcom

What I did
Added support for snat, dnat and ipmc resources under CRM module.

How I did it
New feature NAT adds new resources snat_enty and dnat_entry that needs to be monitored. ipmc_entry tracks IP multicast resources used by switch.

How to verify it
sonic-utilities tests and crm spytest

files/build_templates/init_cfg.json.j2

@@ -11,7 +11,7 @@
             "polling_interval": "300",
 {%- for crm_res in ["ipv4_route", "ipv6_route", "ipv4_nexthop", "ipv6_nexthop", "ipv4_neighbor",
                     "ipv6_neighbor", "nexthop_group_member", "nexthop_group", "acl_table",
-                    "acl_group", "acl_entry", "acl_counter", "fdb_entry"] %}
+                    "acl_group", "acl_entry", "acl_counter", "fdb_entry", "snat_entry", "dnat_entry", "ipmc_entry"] %}
             "{{crm_res}}_threshold_type": "percentage",
             "{{crm_res}}_low_threshold": "70",
             "{{crm_res}}_high_threshold": "85"{% if not loop.last %},{% endif -%}