Document scope for profile section variables

There are several sections in a profile file and the scope of recipes it applies to is not exactly the same: `settings`, `options`, `env`, `build_requires`. By default, `options` apply only to the consumer, while all the others apply to all the references in the graph. This should be documented [[1]](https://docs.conan.io/en/latest/using_packages/using_profiles.html?highlight=profiles) [[2]](https://docs.conan.io/en/latest/reference/profiles.html#profiles). Same for the options/settings that are assigned using the command line.

Related: https://github.com/conan-io/conan/issues/4861