packerv2: warn of hcp_packer_image depreciation

[lbajolet-hashicorp]

🛠️ Description

Since hcp_packer_image is being superseded by hcp_packer_artifact, we warn that it will eventually be removed and that its uses should be updated to use the new data source.

🏗️ Acceptance tests

• Are there any feature flags that are required to use this functionality? - No
• Have you added an acceptance test for the functionality being added? - No
• Have you run the acceptance tests on this branch? - Yes

Output from acceptance testing:

╷
│ Warning: Deprecated Resource
│ 
│   with data.hcp_packer_image.img,
│   on channel_setup.hcl.tf line 18, in data "hcp_packer_image" "img":
│   18: data "hcp_packer_image" "img" {
│ 
│ This data source has been deprecated. Use the new `hcp_packer_artifact`
│ data source instead.
│ 
│ (and one more similar warning elsewhere)
╵

[nywilken]

Good catch.