Check and return errors in the process of determining authentication
configs so that unexpected failures don't occur latter in the process
of build an image or creating a container.

BuildOptions will now return an empty result on error instead of an
incomplete one, to ensure that consumers don't use partial data.

Fix builds with different config or override environments failing when
the authentication configuration changes, which was introduced by #2646.

Report errors from GetRegistryCredentials calls to avoid unexpected
failures latter on in the authentication process.

Split out the functionality to read a Dockerfile from an io.Reader into
ExtractImagesFromReader, as required when processing from a tar archive.

Deprecated function ContainerRequest.GetAuthConfigs will now panic if
an error occurs, so that callers understand that an failure occurred.

Remove unused parameter t from prepareRedisImage.

BREAKING CHANGE Add support for determining the required authentication
in when building an image from a ContextArchive, this requires ContextArchive
support io.Seeker.