[aws-ec2] L2 Construct - VpcPeeringConnection

L2 Construct for `ec2.CfnVpcPeeringConnection`

### Use Case


- To construct a new vpc peering connection.
- To import an existing one.

```
import * as ec2 from '@aws-cdk/aws-ec2'

const vpcPeeringConnection = ec2.VpcPeeringConnection.fromVpcPeeringConnectionAttributes(this, 'vpcPeeringConnection', {
vpcPeeringConnectionId: 'pcx-01234567890abcdef',
});

const vpc: ec2.Vpc = ...

const routes = vpc.privateSubnets
.map((_) => _.routeTable.routeTableId)
.map((routeTableId, index) => {
return new ec2.CfnRoute(this, `route-${index}`, {
destinationCidrBlock: '192.168.0.0/24',
routeTableId,
vpcPeeringConnectionId: vpcPeeringConnection.vpcPeeringConnectionId,
})
})
```

### Proposed Solution

I'll make a pull request.

### Other

* [x] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

---

This is a :rocket: Feature Request

Start by reading the existing AWS CDK EC2 L2 constructs and the ec2.CfnVpcPeeringConnection resource. Use the issue's creation and import examples as the acceptance criteria: the construct should support both operations and expose vpcPeeringConnectionId for routes.

Written by the indexing model from the issue text.