Separate Docker Images From Kpt Release

[runewake2]

Currently Kpt's Docker Images build Kpt from source instead of utilizing a released version of Kpt. This means that in order to ship a new version of the Kpt containers - even if no code changes are made - a new release of Kpt must be triggered. This also introduces duplicate work (we must build kpt for release + once per container we release) and introduces potential for tests to miss coverage in the containerized versions (if we place the Kpt binary we produce under test those tests will either need to be duplicated in the Docker container or a gap will be introduced that leaves the Kpt container binary untested).

This can be improved by installing Kpt from the public releases instead of rebuilding inside the container from source. Alternatively allowing the Kpt version to be pinned separate from the Docker release version would enable us to maintain the Dockerfiles without requiring full Kpt releases.