Build Shared Information Variables

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#### Description

It would be useful to have similar [Build Shared Information Variables](https://developer.hashicorp.com/packer/plugins/builders/amazon/ebs#build-shared-information-variables) that the Amazon EBS provider uses.

#### Use Case(s)

This would be useful for tagging an image with the source image's name.

#### Potential configuration

```
source "googlecompute" "ubuntu-lts" {
project_id = "${var.gcp-project}"
source_image_family = "ubuntu-2204-lts"
image_labels = {
image_source = {{ .SourceImgName }}
}
}
```

#### Potential References