S3 data source

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#### Description

It would be great to have AWS S3 data source in addition to SSM Parameter store and Secrets manager. I can't find any implementations in Packer plugins.

#### Use Case(s)

Our use case is following:
* Create some resources for packer (subnet, security group, etc) using terraform
* Export them to S3 as json object
* Read the data from S3 using packer data source

While this is possible to implement using SSM, we would like not to depend on service we are not using in other production systems. At the moment we are manually copying file from S3 using aws cli, and passing it as vars, while using data source would be easier to use.

#### Potential configuration

```hcl
data "amazon-s3" "basic-example" {
bucket = "acme-bucket"
key = "packer-export/config.json"
}

locals {
body = data.amazon-s3.basic-example.body
version_id = data.amazon-s3.basic-example.version_id
}
```

#### Potential References
https://developer.hashicorp.com/packer/plugins/datasources/amazon/parameterstore
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/s3_object