feat: Add distribution Docker Engine API

[bbartels]

Docker.DotNet did not expose the Docker Engine GET /distribution/{name}/json endpoint, so callers could not inspect registry-backed image metadata without pulling the image first. This change adds a minimal Distribution API surface on IDockerClient for remote descriptor/platform inspection.

• API surface

  • Adds IDistributionOperations with InspectAsync(string name, CancellationToken)
  • Wires Distribution into IDockerClient and DockerClient

• Endpoint implementation

  • Adds DistributionOperations to call distribution/{name}/json
  • Maps 404 responses to DockerImageNotFoundException
  • Follows the existing endpoint pattern used across the client

• Model support

  • Adds DistributionInspectResponse using the existing Descriptor and Platform models
  • Registers the new response type with the source-generated JSON serializer context

• Tests

  • Adds coverage for:
    • successful inspect of alpine:3.20
    • missing manifest/image handling
    • null/empty image name validation

var response = await dockerClient.Distribution.InspectAsync("alpine:3.20", cancellationToken);

var digest = response.Descriptor.Digest;
var platforms = response.Platforms;

[bbartels]

@HofmeisterAn I've been trying to use the distribution api, but wasn't available via the SDK. This PR implements calling out to that api

[campersau]

Looks like the generated code was modified by hand.

You could add the distribution inspect types from here:
https://github.com/moby/moby/blob/a2d62b318ead6553cb591d592aa198808ded3d0b/client/distribution_inspect.go#L13 or
https://github.com/moby/moby/blob/a2d62b318ead6553cb591d592aa198808ded3d0b/api/types/registry/registry.go#L60

into https://github.com/testcontainers/Docker.DotNet/blob/main/tools/specgen/specgen.go

and then regenerated the code.

[bbartels]

Looks like the generated code was modified by hand.

You could add the distribution inspect types from here: https://github.com/moby/moby/blob/a2d62b318ead6553cb591d592aa198808ded3d0b/client/distribution_inspect.go#L13 or https://github.com/moby/moby/blob/a2d62b318ead6553cb591d592aa198808ded3d0b/api/types/registry/registry.go#L60

into https://github.com/testcontainers/Docker.DotNet/blob/main/tools/specgen/specgen.go

and then regenerated the code.

Ah right, amended!

[HofmeisterAn]

Thanks