[CodeBuild] [request]: Pull images through VPC ENI

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**Tell us about your request**
Codebuild can be configured to pull images from a private repository as well as being configured to run in your VPC. But Codebuild always pulls images through the public internet rather than the configured VPC subnet/security group.

Please allow pulling images through a VPC ENI to allow for IP range enforcement/accessing registries on private networks.

**Which service(s) is this request for?**
Codebuild

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Pulling images from a private repository which doesn't allow wide internet access

**Are you currently working around this issue?**
Manually copying images to an ECR

**Additional context**
N/A

**Attachments**
N/A

The request concerns AWS CodeBuild image pulls, private repositories, VPC subnets, security groups, and VPC ENIs; it names no repository files or tests. Start by reviewing the CodeBuild image-pull and VPC configuration entry points. Done means private images can be pulled through the configured VPC ENI while respecting network access controls.

Written by the indexing model from the issue text.