Add chicken or the egg dilemma: Reading deps_cpp_info

Hi!

Eventually some users ask if is it possible to read `self.deps_cpp_info` when running `configure` or `config_options`. As we know, the dependencies graph is not ready yet.

We could include this problem under FAQ or Troubleshooting, using a common example, trying to list some option from a dependency and explaining about the dependencies graph. Actually, Memsharded made a great explanation in some issue, you could copy from there.

Related issues: https://github.com/conan-io/conan/issues/4407 https://github.com/conan-io/conan/issues/2218 https://github.com/conan-io/conan/issues/4450 https://github.com/conan-io/conan/issues/4401

Regards!