Fix Dockerfile not located when added to dockerignore

[danvergara]

What does this PR do?

When the user adds Dockerfile to the .dockerignore file, testcontainers is not able to build the image with error:

Error response from daemon: Cannot locate specified Dockerfile

This is because testcontainers doesn't include the Dockerfile to the buildcontext on purpose, it only expects to do so, if it is not included on the ignorefile. The docker client doesn't this either, the Docker cli is aware of this and maintainers have addressed this limitation in this PR long ago as the have tweaked the client to include both files to the build context.

To fix this, I added the .dockerignore file in the current context and the target Dockefile to the Build Context.

includes = append(includes, dockerIgnoreLocation, c.GetDockerfile())

archive.TarOptions struct has a key on it to include files to the archive:

buildContext, err := archive.TarWithOptions(
	c.Context,
	&archive.TarOptions{ExcludePatterns: excluded, IncludeFiles: includes},
)

Why is it important?

The motivation is that some developers don't want to include the Dockerfile to the result image to keep it as minimal as possible.

Related issues

Closes #2203

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[danvergara]

@mdelapenya is it normal that the Rootless pipeline always fails? I keep seeing it failing across the latest pull requests.

[mdelapenya]

LGTM, thanks for investigating and submitting a fix. Much appreciated!