fix(ecs): unclear docs on valid ec2 task definition placement constraints and no validation of input #25933 (#26384)

Docs were unclear on valid placement constraints. You can specify distinctInstances when creating a Service, or running a task. You can specify memberOf when doing the previous two actions, or when creating a task or new revision. So far only memberOf is valid for ec2 task definitions.

This pull request enhances the documentation and validation for task definition placement constraints in the aws-cdk-lib/aws-ecs package. The documentation now includes a note clarifying the valid placement constraints and a new validatePlacementConstraints method has been added to the Ec2TaskDefinition class to validate the constraints at synth time.

The changes include:

Enhancement of documentation in ec2-task-definition.ts to include a note about valid placement constraints.
Addition of the validatePlacementConstraints method in ec2-task-definition.ts to validate placement constraints at synth time.
Addition of unit tests in ec2-task-definition.test.ts to verify the correct behavior of the new validatePlacementConstraints method.
Addition of integration tests to ensure overall functionality.
Closes #25905.

Revival of #25933

----

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

Author: Adibuer-lab

package.json

@@ -173,4 +173,4 @@
   "dependencies": {
     "string-width": "^4.2.3"
   }
-}
+}

packages/@aws-cdk-testing/framework-integ/test/aws-ecs/test/ec2/integ.task-definition-placement-constraints.js.snapshot/asset.ba598c1f1d84f7077ea9c16a6b921e4f8acf18e996100e72a8f17da980e64fdd/__entrypoint__.js

@@ -0,0 +1,32 @@
+{
+  "version": "32.0.0",
+  "files": {
+    "ba598c1f1d84f7077ea9c16a6b921e4f8acf18e996100e72a8f17da980e64fdd": {
+      "source": {
+        "path": "asset.ba598c1f1d84f7077ea9c16a6b921e4f8acf18e996100e72a8f17da980e64fdd",
+        "packaging": "zip"
+      },
+      "destinations": {
+        "current_account-current_region": {
+          "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
+          "objectKey": "ba598c1f1d84f7077ea9c16a6b921e4f8acf18e996100e72a8f17da980e64fdd.zip",
+          "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
+        }
+      }
+    },
+    "0a9ca3828434fca52688d82a6c9438b44fc25f418219dcc41eefa938e401e99b": {
+      "source": {
+        "path": "aws-cdk-ecs-integration-test-stack.template.json",
+        "packaging": "file"
+      },
+      "destinations": {
+        "current_account-current_region": {
+          "bucketName": "cdk-hnb659fds-assets-${AWS::AccountId}-${AWS::Region}",
+          "objectKey": "0a9ca3828434fca52688d82a6c9438b44fc25f418219dcc41eefa938e401e99b.json",
+          "assumeRoleArn": "arn:${AWS::Partition}:iam::${AWS::AccountId}:role/cdk-hnb659fds-file-publishing-role-${AWS::AccountId}-${AWS::Region}"
+        }
+      }
+    }
+  },
+  "dockerImages": {}
+}