Implement bp2build converter for rust_protobuf_host

Test: go test
Bug: 295925256
Change-Id: I43b7359da8fc19f4338e2583448b7617194df5e6
diff --git a/rust/rust.go b/rust/rust.go
index 9494507..1ee99cd 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -1852,6 +1852,8 @@
 		procMacroBp2build(ctx, m)
 	} else if ctx.ModuleType() == "rust_binary_host" {
 		binaryBp2build(ctx, m)
+	} else if ctx.ModuleType() == "rust_protobuf_host" {
+		protoLibraryBp2build(ctx, m)
 	} else {
 		ctx.MarkBp2buildUnconvertible(bp2build_metrics_proto.UnconvertedReasonType_TYPE_UNSUPPORTED, "")
 	}