CRAS: libcras: update rust client to split shm

Switches the rust cras client to use a split shm instead of one shm area for
both header and samples.

Also updates cras_shm.rs to use some of the generated rust code from cras_shm.h
instead of copying it manually in rust.

BUG=chromium:968724
TEST=rust unit tests, cras_tests playback/recording on device

Change-Id: I8e468d17e11a025c2c7b062f323ddf11ab8c7001
Reviewed-on: https://chromium-review.googlesource.com/1663170
Tested-by: Fletcher Woodruff <fletcherw@chromium.org>
Commit-Ready: Fletcher Woodruff <fletcherw@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Chih-Yang Hsia <paulhsia@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
4 files changed