Updated 7260 64x100 MMU Profile. (#7849)

What I did:

Updated 7260 MMU Profile based on latest MSFT Tier 1 Tomahawk2_MMU_Setting_48x100G_40m_16x100G_300m_v1.0 and
TH2_PGHdrm_MSFT.

How I verify:
Made sure image is up/traffic is flowing/mmu dump looked fine.
SAI qos test need will be updated to support this SKU.

Author: abdosi

device/arista/x86_64-arista_7260cx3_64/Arista-7260CX3-C64/buffers_defaults_t1.j2

@@ -10,18 +10,22 @@
 {%- macro generate_buffer_pool_and_profiles() %}
     "BUFFER_POOL": {
         "ingress_lossless_pool": {
-            "size": "33329088",
+            {# SS Tab2 Row 71 #}
+            "size": "33582016",
             "type": "ingress",
             "mode": "dynamic",
-            "xoff": "7827456"
+            {# SS Tab2 Row 68 #}
+            "xoff": "8965632"
         },
         "egress_lossy_pool": {
-            "size": "26663272",
+            {# SS Tab2 Row 60 #}
+            "size": "26866112",
             "type": "egress",
             "mode": "dynamic"
         },
         "egress_lossless_pool": {
-            "size": "42349632",
+            {# SS Tab2 Row 56 #}
+            "size": "43481152",
             "type": "egress",
             "mode": "static"
         }
@@ -30,12 +34,14 @@
         "ingress_lossy_profile": {
             "pool":"[BUFFER_POOL|ingress_lossless_pool]",
             "size":"0",
+            {# SS Tab1 Row 9 #}
             "static_th":"44302336"
         },
         "egress_lossless_profile": {
             "pool":"[BUFFER_POOL|egress_lossless_pool]",
             "size":"0",
-            "static_th":"42349632"
+            {# SS Tab2 Row 56 #}
+            "static_th":"43481152"
         },
         "egress_lossy_profile": {
             "pool":"[BUFFER_POOL|egress_lossy_pool]",

device/arista/x86_64-arista_7260cx3_64/Arista-7260CX3-C64/pg_profile_lookup.ini

@@ -1,8 +1,5 @@
 # PG lossless profiles.
 # speed cable size    xon  xoff     threshold xon_offset
-  50000  5m   1248    1248 56160    -3        2496
- 100000  5m   1248    1248 96928    -3        2496
-  50000  40m  1248    1248 96096    -3        2496
- 100000  40m  1248    1248 177632   -3        2496
-  50000  300m 1248    1248 141856   -3        2496
- 100000  300m 1248    1248 268736   -3        2496
+ 100000  5m   1248    1248 96928     -3        2496
+ 100000  40m  1248    1248 59696     -3        2496
+ 100000  300m 1248    1248 101088    -3        2496