Added Consistent No Prelude Attribute RFC

Make name and behavior of the `#![no_std]` and `#![no_implicit_prelude]` attributes
consistent by renaming the latter to `#![no_prelude]` and having it only apply to the current
module.

Optionally add a `#[deep(...)]` attribute for deeply applying an attribute to each module as
composable replacement for the old behavior.

[](Rendered)