[feature] fastbuild support

[dev-joss]

Support fastbuild .bff generation for integration with fastbuild build system. https://www.fastbuild.org/docs/home.html

• [x] I've read the CONTRIBUTING guide.

[dev-joss]

Similar to visual studio .props files, I would expect conan to generate a .bff file with variables populated with the various dependency paths

[memsharded]

As we are lacking FastBuild expertise, I'd recommend interested users on this build system to give it a try, and set up a repo that contains a package recipe intended to be python_required with:

• A FastBuildDeps generator
• A FastBuildToolchain generator
• A FastBuild command wrapper

We might be able to give feedback and guidance, but it is unlikely that we will be able to put time in this after 2.0 (2.X), and that is a few months from now.