[Arista] Add other chassis names to platform_components.json for 720DT-48S (#12378)

Why I did it
The 720DT-48S platform has variants with different chassis names, and these need to all be included in platform_components.json to ensure that sonic-mgmt platform_tests/fwutil/test_fwutil.py::test_fwutil_show passes

How I did it
Updated platform_components.json with the variant names for 720DT-48S.

How to verify it
Ran aforementioned testcase and verified that it passes on the different variants.

Author: andywongarista

device/arista/x86_64-arista_720dt_48s/platform_components.json

@@ -5,6 +5,18 @@
                 "Aboot()": {},
                 "Scd(addr=0000:00:18.7)": {}
             }
+        },
+        "CCS-720DT-48S-2F": {
+            "component": {
+                "Aboot()": {},
+                "Scd(addr=0000:00:18.7)": {}
+            }
+        },
+        "CCS-720DT-48S-2R": {
+            "component": {
+                "Aboot()": {},
+                "Scd(addr=0000:00:18.7)": {}
+            }
         }
     }
 }