Add platform.json configs for all denali SKUs (#9717)

device/arista/x86_64-arista_7800_sup/platform.json

@@ -0,0 +1,12 @@
+{
+    "chassis": {
+        "name": "DCS-7800A-SUP1A",
+        "components": [],
+        "fans": [],
+        "fan_drawers": [],
+        "psus": [],
+        "thermals": [],
+        "sfps": []
+    },
+    "interfaces": {}
+}

device/arista/x86_64-arista_7800r3_48cq2_lc/platform.json

@@ -0,0 +1,173 @@
+{
+    "chassis": {
+        "name": "7800R3-48CQ2-LC",
+        "components": [],
+        "fans": [],
+        "fan_drawers": [],
+        "psus": [],
+        "thermals": [
+            {
+                "name": "Cpu temp sensor"
+            },
+            {
+                "name": "Center back"
+            },
+            {
+                "name": "Fap0 core0"
+            },
+            {
+                "name": "Fap0 core1"
+            },
+            {
+                "name": "PCIE"
+            }
+        ],
+        "sfps": [
+            {
+                "name": "qsfp1"
+            },
+            {
+                "name": "qsfp2"
+            },
+            {
+                "name": "qsfp3"
+            },
+            {
+                "name": "qsfp4"
+            },
+            {
+                "name": "qsfp5"
+            },
+            {
+                "name": "qsfp6"
+            },
+            {
+                "name": "qsfp7"
+            },
+            {
+                "name": "qsfp8"
+            },
+            {
+                "name": "qsfp9"
+            },
+            {
+                "name": "qsfp10"
+            },
+            {
+                "name": "qsfp11"
+            },
+            {
+                "name": "qsfp12"
+            },
+            {
+                "name": "qsfp13"
+            },
+            {
+                "name": "qsfp14"
+            },
+            {
+                "name": "qsfp15"
+            },
+            {
+                "name": "qsfp16"
+            },
+            {
+                "name": "qsfp17"
+            },
+            {
+                "name": "qsfp18"
+            },
+            {
+                "name": "qsfp19"
+            },
+            {
+                "name": "qsfp20"
+            },
+            {
+                "name": "qsfp21"
+            },
+            {
+                "name": "qsfp22"
+            },
+            {
+                "name": "qsfp23"
+            },
+            {
+                "name": "qsfp24"
+            },
+            {
+                "name": "qsfp25"
+            },
+            {
+                "name": "qsfp26"
+            },
+            {
+                "name": "qsfp27"
+            },
+            {
+                "name": "qsfp28"
+            },
+            {
+                "name": "qsfp29"
+            },
+            {
+                "name": "qsfp30"
+            },
+            {
+                "name": "qsfp31"
+            },
+            {
+                "name": "qsfp32"
+            },
+            {
+                "name": "qsfp33"
+            },
+            {
+                "name": "qsfp34"
+            },
+            {
+                "name": "qsfp35"
+            },
+            {
+                "name": "qsfp36"
+            },
+            {
+                "name": "qsfp37"
+            },
+            {
+                "name": "qsfp38"
+            },
+            {
+                "name": "qsfp39"
+            },
+            {
+                "name": "qsfp40"
+            },
+            {
+                "name": "qsfp41"
+            },
+            {
+                "name": "qsfp42"
+            },
+            {
+                "name": "qsfp43"
+            },
+            {
+                "name": "qsfp44"
+            },
+            {
+                "name": "qsfp45"
+            },
+            {
+                "name": "qsfp46"
+            },
+            {
+                "name": "qsfp47"
+            },
+            {
+                "name": "qsfp48"
+            }
+        ]
+    },
+    "interfaces": {}
+}

device/arista/x86_64-arista_7800r3_48cqm2_lc/platform.json

@@ -0,0 +1 @@
+../x86_64-arista_7800r3_48cq2_lc/platform.json