- Add build scripts for Rust flatbuffers.
- Rewrites some reply.cc methods in Rust.
- Changes some struct elements to table in msg.fbs (rust flatbuffers
lacks support currently)
- Renames handlers_test to test_rs.
- This reorg is needed to make progress on the code cache handler.
Move rust.gni and deno.gni into build_extra/
Removes rust_library which was only an action. This instead defines
rust_component, which is an action plus a gn "component" target
to expose the resulting object file. This simplifies link code in
rust.gni.
Support rust modules that can be linked into C++.