Review Console reference management

[lionel-]

Branched from #1100
Progress towards #1145

• New Console::with() that passes a Console ref and catches panics, transforming them to Result.

• Console::get() pushed to the FFI boundary and abstracted with [ark::register]. This new macro wraps [harp::register] and calls Console::with(). Any panics due to e.g. RefCell issues gets converted to an R error.

• The graphics callbacks are migrated to [ark::register], but all Ark FFI entries should use it in the future.

• DeviceContext no longer reaches back into Console. It stores all needed state on itself.

• PlotComm also owns what it needs. I was wrong to pass &Console to all handlers. PlotComm is the only CommHandler that used &Console, just to get the device_context(). It now holds an Rc<DeviceContext> passed at construction time.

• All methods in console_comm.rs now take &self. Supported by a take/remove pattern. Also the comms are now stored in a DebugRefCell, a new type that maps to RefCell in debug builds and to UnsafeCell (with logging) in release builds. This allows us to transition to more Rust safety without causing panics in release builds, and without having to handle panics in awkward places.