Add VPC endpoint return values to AWS::Transfer::Server return values

### Name of the resource

AWS::Transfer::Server

### Resource name

_No response_

### Description

`AWS::Transfer::Server` automatically creates a VPC endpoint when using `EndpointType: VPC`. However it does not have any references to the VPC endpoint it creates in its return values. We have a need to create a route53 record for the VPC endpoint and at the moment the only way we could think of how to do this is via querying VPC endpoints, filtering for endpoints with the service name transfer.server and finally going through that list to match one that has a security group attached to it with a name we can control. We cannot sort with tags as vpc endpoint tags aren't supported in cloudformation either.

We also have not found a way to manually configure a VPC endpoint and attach that to the transfer server. With the now deprecated `EndpointType: VPC_ENDPOINT` you could supply it with `EndpointDetails` -> `VpcEndpointId`. But there seems to be no way of using a user configured VPC endpoint with the current EndpointType. If we were able to create our own VPC endpoint we could then use its return value which would also be a satisfactory enhancement.

### Other Details

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-transfer-server.html#aws-resource-transfer-server-return-values
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-transfer-server-endpointdetails.html#cfn-transfer-server-endpointdetails-vpcendpointid

Review the AWS::Transfer::Server return values and EndpointDetails documentation linked in the issue. Compare exposing the automatically created VPC endpoint with allowing a user-configured endpoint, then clarify the desired CloudFormation behavior and acceptance criteria. Done means the requested endpoint can be referenced for Route 53 integration or configured explicitly.

Written by the indexing model from the issue text.