Rust protobuf 2->3: Update Bluetooth

tldr: remove protobuf2 from Android Rust and upgrade everything to pb3.

These commits update:
- The grpcio rust crate to use protobuf 3
- The build system to always use the new libprotobuf (pb3) instead of the _deprecated variant (for pb2); they also force-enable libprotobuf everywhere, ignoring the use_protobuf3 flag, removes the tests related to pb2
- The following modules, which required syntax changes:
-- packages/modules/Bluetooth
-- device/google/cuttlefish
-- vendor/auto

Bug: 308790516
Test: m rust
Flag: EXEMPT 3p rust crate upgrade

Change-Id: I6f4589dcf503f3a360c3bc4ade7844e858ed618e

1 files changed, 4 insertions, 0 deletions

diff --git a/build.py b/build.py
index 388ec46a13..5e03c6388c 100755
--- a/build.py
+++ b/build.py
@@ -268,6 +268,10 @@ class HostBuild():
         self.custom_env['CXX_ROOT_PATH'] = os.path.join(self.platform_dir, 'bt')
         self.custom_env['CROS_SYSTEM_API_ROOT'] = os.path.join(self.platform_dir, 'system_api')
         self.custom_env['CXX_OUTDIR'] = self._gn_default_output()
+
+        # On ChromeOS, this is /usr/bin/grpc_rust_plugin
+        # In the container, this is /root/.cargo/bin/grpc_rust_plugin
+        self.custom_env['GRPC_RUST_PLUGIN_PATH'] = shutil.which('grpc_rust_plugin')
         self.env.update(self.custom_env)
 
     def print_env(self):