Remove code duplication in Dockerfile

All the Dockerfiles for the different binaries are nearly identical

e.g.
https://github.com/kubeflow/katib/blob/master/cmd/metricscollector/Dockerfile
https://github.com/kubeflow/katib/blob/master/cmd/studyjobcontroller/Dockerfile

Instead of duplicating the Dockerfiles can we just have a single Dockerfile that takes a BuildArg specifying the binary?

Start by comparing cmd/metricscollector/Dockerfile and cmd/studyjobcontroller/Dockerfile, then inspect the other binary Dockerfiles for the shared pattern. Determine how each image selects its binary and how builds are invoked. Done means the duplicated Dockerfiles are replaced by a shared Dockerfile accepting a BuildArg for the binary, with all affected images still buildable.

Written by the indexing model from the issue text.