Align OCI artifacts with upstream guidance

[neersighted]

• Relates to implement publish #11008

What I did

Make some slight tweaks to the code that produces and consumes Compose files as OCI artifacts in order to align with upstream best practices/the official guidance.

Manifest before:

{
        "schemaVersion": 2,
        "mediaType": "application/vnd.oci.image.manifest.v1+json",
        "artifactType": "application/vnd.docker.compose.project",
        "config": {
                "mediaType": "application/vnd.docker.compose.project",
                "digest": "sha256:44136fa355b3678a1146ad16f7e8649e94fb4fc21fe77e8310c060f61caaff8a",
                "size": 2,
                "annotations": {
                        "com.docker.compose.version": "2.22.0"
                }
        },
        "layers": [
                {
                        "mediaType": "application/vnd.docker.compose.file+yaml",
                        "digest": "sha256:839ee3e27293c4f021ad49d8e71ec85bfc69706d1f06037b848a4f13564eeba8",
                        "size": 343,
                        "annotations": {
                                "com.docker.compose": "2.22.0"
                        }
                }
        ]
}

Manifest after:

{
        "schemaVersion": 2,
        "mediaType": "application/vnd.oci.image.manifest.v1+json",
        "artifactType": "application/vnd.docker.compose.project",
        "config": {
                "mediaType": "application/vnd.oci.empty.v1+json",
                "digest": "sha256:44136fa355b3678a1146ad16f7e8649e94fb4fc21fe77e8310c060f61caaff8a",
                "size": 2
        },
        "layers": [
                {
                        "mediaType": "application/vnd.docker.compose.file+yaml",
                        "digest": "sha256:839ee3e27293c4f021ad49d8e71ec85bfc69706d1f06037b848a4f13564eeba8",
                        "size": 343,
                        "annotations": {
                                "com.docker.compose.version": "2.22.0"
                        }
                }
        ]
}

Related issue
N/A

[ndeloof]

👍

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (bd74a92) 57.44% compared to head (6dcdcc2) 57.57%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11049      +/-   ##
==========================================
+ Coverage   57.44%   57.57%   +0.13%     
==========================================
  Files         129      129              
  Lines       11232    11229       -3     
==========================================
+ Hits         6452     6465      +13     
+ Misses       4149     4135      -14     
+ Partials      631      629       -2     

Files	Coverage Δ
pkg/compose/publish.go	0.00% <0.00%> (ø)
pkg/remote/oci.go	2.38% <0.00%> (ø)

... and 5 files with indirect coverage changes

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