Instead of using the miniconda2 EUPS product. newinstall.sh should directly install the conda env similar to lsstsw/bin/deploy.

This will solve multiple problems:

• Removes the requirement that the installation env already has a working python installation regardless of whether or not we are installing miniconda.
• Removes the need for the miniconda2/3 EUPS products which need to be manually updated and are not tagged as part of a regular release as they are outside the dep chain.
• Works around py2 packages leaking into the EUPS python env, which has been observed to cause a failure when installing py2 tarball products into an EUPS env running under py3.