Add customization for EC2 legacy dualstack endpoints (#3967)

Author: trivikr

.changes/next-release/bugfix-EC2-a3dc85ca.json

@@ -0,0 +1,5 @@
+{
+  "type": "bugfix",
+  "category": "EC2",
+  "description": "Add customization for EC2 legacy dualstack endpoints"
+}

lib/region_config_data.json

@@ -127,10 +127,18 @@
     "cn-*/*": {
       "endpoint": "{service}.{region}.api.amazonwebservices.com.cn"
     },
+
     "*/s3": "dualstackLegacy",
     "cn-*/s3": "dualstackLegacyCn",
     "*/s3-control": "dualstackLegacy",
-    "cn-*/s3-control": "dualstackLegacyCn"
+    "cn-*/s3-control": "dualstackLegacyCn",
+
+    "ap-south-1/ec2": "dualstackLegacyEc2",
+    "eu-west-1/ec2": "dualstackLegacyEc2",
+    "sa-east-1/ec2": "dualstackLegacyEc2",
+    "us-east-1/ec2": "dualstackLegacyEc2",
+    "us-east-2/ec2": "dualstackLegacyEc2",
+    "us-west-2/ec2": "dualstackLegacyEc2"
   },
 
   "dualstackFipsRules": {
@@ -202,6 +210,9 @@
     },
     "dualstackFipsLegacyCn": {
       "endpoint": "{service}-fips.dualstack.{region}.amazonaws.com.cn"
+    },
+    "dualstackLegacyEc2": {
+      "endpoint": "api.ec2.{region}.aws"
     }
   }
 }

test/endpoint/test_cases_supported.json

@@ -2439,6 +2439,14 @@
     "useDualstackEndpoint": false,
     "hostname": "ec2-fips.af-south-1.amazonaws.com"
   },
+  {
+    "endpointPrefix": "ec2",
+    "clientName": "EC2",
+    "region": "ap-south-1",
+    "useFipsEndpoint": false,
+    "useDualstackEndpoint": true,
+    "hostname": "api.ec2.ap-south-1.aws"
+  },
   {
     "endpointPrefix": "ec2",
     "clientName": "EC2",

test/endpoint/test_cases_unsupported.json

@@ -80,14 +80,6 @@
     "useDualstackEndpoint": false,
     "hostname": "data.iot-fips.us-gov-east-1.amazonaws.com"
   },
-  {
-    "endpointPrefix": "ec2",
-    "clientName": "EC2",
-    "region": "ap-south-1",
-    "useFipsEndpoint": false,
-    "useDualstackEndpoint": true,
-    "hostname": "api.ec2.ap-south-1.aws"
-  },
   {
     "endpointPrefix": "dms",
     "clientName": "DMS",