Amplify Hosting Service Public IP Range

### Before opening, please confirm:

- [X] I have checked to see if my question is addressed in the [FAQ](https://github.com/aws-amplify/amplify-hosting/blob/master/FAQ.md).
- [X] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-hosting/issues?q=is%3Aissue+).
- [X] I have read the guide for [submitting questions](https://github.com/aws-amplify/amplify-hosting/blob/master/CONTRIBUTING.md).
- [X] I have removed any sensitive information from my code snippets and submission.

### App Id

NEW_APP

### AWS Region

us-east-1

### Amplify Hosting feature

Backend builds

### Is your feature request related to a problem? Please describe:

Can't connect to the repository if the organization enables IP allow list in Bitbucket or Github Enterprise to restrict the access.

### Describe how you'd like this feature to work

Like other AWS services, provide an IP range so that the repository or other external services can whitelist these IP addresses.

Start by reviewing FAQ.md and CONTRIBUTING.md, then investigate how Amplify Hosting backend builds connect to Bitbucket or GitHub Enterprise. The issue does not name implementation files or tests; done would mean defining and delivering a usable public IP range that external repository services can whitelist.

Written by the indexing model from the issue text.