Enhancement: Reduce Windows image size

[jrbe228]

The current Dockerfile includes a COPY step on line 5.

By copying installer binaries using this method, the binary adds several unnecessary GB to the final image. Consider other approaches using RUN instead of COPY. Within a single RUN step,

1. Download the installer binary from a company web server. Perform installation. Delete the binary.
2. Same as above, except generating / removing a local network share.
3. BuildKit for Windows is now in early release. I haven't used it and can't comment on stability or ease of use. But eventually this should become the preferred approach.