Fuchsia's Integration Interface: fint

Fuchsia's integration interface is the interface between the Fuchsia platform and any infrastructure that builds and tests Fuchsia. It is encapsulated as the interface of the tool fint (/'fɪnt/, fuchsia integration).

TODO(fxbug.dev/10428, fxbug.dev/10429): fint is under simulateous and iterative design and developement. As it is extended, keep its interface documented and up-to-date here.