[202205][Buffer] Added cable length config to buffer config template for EdgeZoneAggregator (sonic-net#14538)

Why I did it
SONiC currently does not identify 'EdgeZoneAggregator' neighbor. As a result, the buffer profile attached to those interfaces uses the default cable length which could cause ingress packet drops due to insufficient headroom. Hence, there is a need to update the buffer templates to identify such neighbors and assign the same cable length as used by the T1.

How I did it
Modified the buffer template to identify EdgeZoneAggregator as a neighbor device type and assign it the same cable length as a T1/leaf router.

How to verify it
Unit tests pass, and manually checked on a 7260 to see the changes take effect.

Author: developfast

files/build_templates/buffers_config.j2

@@ -53,6 +53,9 @@ def
             {%- if DEVICE_NEIGHBOR_METADATA is defined and DEVICE_NEIGHBOR_METADATA[DEVICE_NEIGHBOR[local_port].name] %}
                 {%- set neighbor = DEVICE_NEIGHBOR_METADATA[DEVICE_NEIGHBOR[local_port].name] %}
                 {%- set neighbor_role = neighbor.type %}
+                {%- if 'edgezoneaggregator' == neighbor_role | lower %}
+                         {%- set neighbor_role = 'LeafRouter' %}
+                {%- endif %}
                 {%- if 'asic' == neighbor_role | lower %}
                          {%- set roles1 = 'internal' %}
                          {%- if 'internal' not in ports2cable %}