Generator roles

[tbinna]

I am creating this post to record the general idea of the existing generators:

• Starting from Nx18, init generators are called by nx add. They are expected to set up the minimum required dependencies for the plugin to work.
• Init generators should not call other init generators
• Most dependencies are only needed and can be installed by the generators invoking the init generators

Refer to this PR for details: nrwl/nx#21088:

The init generators were always internal and meant to be called by other generators to ensure the base dependencies and configuration were set up. This is changing. While they'll continue to be internal, soon they could also be invoked when running nrwl/nx#20976 and nrwl/nx#20872. In those scenarios, we only need to initialize the minimum required for the plugin to work. We wouldn't be generating anything just yet and can't make assumptions and install/configure things that might not be needed by the workspace.