add: TarPath parameter to the build command

[JonasKs]

Status: I’ve opened a PR in the crossplane repo as requested on Slack. See https://github.com/crossplane/crossplane/pull/4741

Let me know if you want this to be updated or closed. 😊

Description of your changes

Add a --tar-path parameter, which is an alternative to --controller. This allow us to use podman in our pipelines. Example working flow:

podman build .
      --file ci/docker/Dockerfile
      --tag $IMAGE_NAME:latest
podman save -o local_image.tar $IMAGE_NAME:latest
./up xpkg build
      --package-root package
      --tar-path local_image.tar
      --output my_provider.xpkg

Fixes #385

I have:

• [x] Read and followed Upbound's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] Added backport release-x.y labels to auto-backport this PR, as appropriate.

How has this code been tested

We have tested a locally built binary, uploaded to a private s3 bucket in a GitLab CI pipeline, using podman, and it works as expected.

[Upbound-CLA]

All committers have signed the CLA.