feat(ec2-alpha): implement mapPublicIpOnLaunch prop in SubnetV2 (#34057)

### Issue # (if applicable)

Closes #32159 .

### Reason for this change

Adding support for `mapPublicIpOnLaunch` prop in SubnetV2.

### Description of changes

Added property mapPublicIpOnLaunch in SubnetV2Props, set to undefined by default.

### Describe any new or updated permissions being added

NA


### Description of how you validated changes

Added unit test and integration tests

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

Author: shikha372

packages/@aws-cdk/aws-ec2-alpha/README.md

@@ -43,6 +43,7 @@ new VpcV2(this, 'Vpc', {
 `SubnetV2` is a re-write of the [`ec2.Subnet`](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_ec2.Subnet.html) construct.
 This new construct can be used to add subnets to a `VpcV2` instance:
 Note: When defining a subnet with `SubnetV2`, CDK automatically creates a new route table, unless a route table is explicitly provided as an input to the construct.
+To enable the `mapPublicIpOnLaunch` feature (which is `false` by default), set the property to `true` when creating the subnet.
 
 ```ts
 const stack = new Stack();
@@ -57,7 +58,8 @@ new SubnetV2(this, 'subnetA', {
   availabilityZone: 'us-east-1a',
   ipv4CidrBlock: new IpCidr('10.0.0.0/24'),
   ipv6CidrBlock: new IpCidr('2a05:d02c:25:4000::/60'),
-  subnetType: SubnetType.PRIVATE_ISOLATED,
+  subnetType: SubnetType.PUBLIC,
+  mapPublicIpOnLaunch: true,
 })
 ```
 

packages/@aws-cdk/aws-ec2-alpha/lib/subnet-v2.ts

@@ -96,6 +96,14 @@ export interface SubnetV2Props {
    */
   readonly assignIpv6AddressOnCreation?: boolean;
 
+  /**
+   * Controls if instances launched into the subnet should be assigned a public IP address.
+   * This property can only be set for public subnets.
+   *
+   * @default - undefined in case not provided as an input
+   */
+  readonly mapPublicIpOnLaunch?: boolean;
+
 }
 
 /**
@@ -276,12 +284,17 @@ export class SubnetV2 extends Resource implements ISubnetV2 {
       throw new Error('IPv6 CIDR block is required when assigning IPv6 address on creation');
     }
 
+    if (props.mapPublicIpOnLaunch === true && props.subnetType !== SubnetType.PUBLIC) {
+      throw new Error('mapPublicIpOnLaunch can only be set to true for public subnets');
+    }
+
     const subnet = new CfnSubnet(this, 'Subnet', {
       vpcId: props.vpc.vpcId,
       cidrBlock: ipv4CidrBlock,
       ipv6CidrBlock: ipv6CidrBlock,
       availabilityZone: props.availabilityZone,
       assignIpv6AddressOnCreation: props.assignIpv6AddressOnCreation ?? false,
+      mapPublicIpOnLaunch: props.mapPublicIpOnLaunch ?? undefined,
     });
 
     this.node.defaultChild = subnet;