Demos bundles: support minify customization

[mpreyskurantov]

Build SystemJs frameworks modules bundles without minification by default (aka dev env). Minify on a flag only. We will need this on another CI, but could test here on GHA as well. Most of the affected files are highlighted with dummy useful changes. Note that the Angular's always non-minified

Nice to have: Support removing a timestamp from a particular module inside a bundle