feat(common): Rust infrastructure

Relates to #5069.

This establishes a baseline Rust build environment and linkage with
common/core/desktop.

This includes:

* build script build.sh which handles builds on Windows, macOS, *nix,
  with multiple targets on Windows only at present (M1 on mac to come
  when we do the mac integration work.)
* a mock rust processor with a very stubbed-out implementation
* bare bones interface between Rust library and C++ code
* unit tests on Rust and integration tests on C++ side to test the
  linkage between the libraries.

This should deliver a set of libraries that can be linked into our
target applications. For ease of deployment, it may be best to make
these static libraries, but I haven't made that decision at this point.