chore(ec2): deprecate security group name accessor (#16116)

The security group name accessor will (almost) always return the security group ID, rather than the name. This change deprecates the name accessor to make it clearer to users that this is not a supported use case.

fixes #13774

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packages/@aws-cdk/aws-ec2/lib/security-group.ts

@@ -382,6 +382,7 @@ export class SecurityGroup extends SecurityGroupBase {
    * An attribute that represents the security group name.
    *
    * @attribute
+   * @deprecated returns the security group ID, rather than the name.
    */
   public readonly securityGroupName: string;