S3 Virtual Hosted Style Urls

s3:: sources: support virtual-hosted-style URLs

s3:: source URLs using the virtual-hosted-style S3 endpoint format were rejected:

terraform {
  source = "s3::https://my-bucket.s3.us-west-2.amazonaws.com/terraform/modules/myapp.zip"
}

This resulted in errors like:

ERROR downloading source url s3::https://my-bucket.s3.us-west-2.amazonaws.com/...
* URL is not a valid S3 URL

Terragrunt now accepts every AWS S3 endpoint form, including virtual-hosted-style URLs (<bucket>.s3.<region>.amazonaws.com) and modern path-style URLs (s3.<region>.amazonaws.com).