feat: Save tiller logs into a file for help with debugging

Related issue: gitlab-org/gitlab#43653 (closed)

When we have a failure like gitlab-org/gitlab#118598 (closed), we want more information to debug

This alters the binary to pipe all tiller output to a file (vs /dev/null). We can then save that file to artifacts on failure.

You can see a sample failed job in https://gitlab.com/gitlab-org/cluster-integration/cluster-applications/-/jobs/382728095

• tiller__2_.log