Deprecate non-standard (config) fields in image inspect output

[thaJeztah]

• relates to https://github.com/moby/moby/pull/47941

The Config field returned by this endpoint (used for "image inspect") returns additional fields that are not part of the image's configuration and not part of the Docker Image Spec and the OCI Image Spec.

These additional fields are included in the response, due to an implementation detail, where the api/types.ImageInspec type used for the response is using the container.Config type.

The container.Config type is a superset of the image config, and while the image's Config is used as a template for containers created from the image, the additional fields are set at runtime (from options passed when creating the container) and not taken from the image Config.

These fields are never set (and always return the default value for the type), but are not omitted in the response when left empty. As these fields were not intended to be part of the image configuration response, they are deprecated, and will be removed from the API.

The following fields are currently included in the API response, but are not part of the underlying image's Config, and deprecated:

• Hostname
• Domainname
• AttachStdin
• AttachStdout
• AttachStderr
• Tty
• OpenStdin
• StdinOnce
• Image
• NetworkDisabled (already omitted unless set)
• MacAddress (already omitted unless set)
• StopTimeout (already omitted unless set)

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Deprecate non-standard (config) fields in image inspect output

The `Config` field returned by this endpoint (used for "image inspect") returns
additional fields that are not part of the image's configuration and not part of
the [Docker Image Spec] and the [OCI Image Spec].

These fields are never set (and always return the default value for the type),
but are not omitted in the response when left empty. As these fields were not
intended to be part of the image configuration response, they are deprecated,
and will be removed from the API.

The following fields are currently included in the API response, but
are not part of the underlying image's Config, and deprecated:

- `Hostname`
- `Domainname`
- `AttachStdin`
- `AttachStdout`
- `AttachStderr`
- `Tty`
- `OpenStdin`
- `StdinOnce`
- `Image`
- `NetworkDisabled` (already omitted unless set)
- `MacAddress` (already omitted unless set)
- `StopTimeout` (already omitted unless set)

[Docker image spec]: https://github.com/moby/docker-image-spec/blob/v1.3.1/specs-go/v1/image.go#L19-L32
[OCI Image Spec]: https://github.com/opencontainers/image-spec/blob/v1.1.0/specs-go/v1/config.go#L24-L62

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 61.79%. Comparing base (0022fe7) to head (b79d684).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5142 +/- ## ========================================== - Coverage 61.82% 61.79% -0.03% ========================================== Files 298 295 -3 Lines 20730 20725 -5 ========================================== - Hits 12817 12808 -9 - Misses 7000 7002 +2 - Partials 913 915 +2 ```

[thaJeztah]

@dvdksn this LGTY?

[thaJeztah]

Let me bring this one in; but happy to make follow-up changes