api: controller/sysroot: PackageIndexInfo deserialization

Switch PackageIndexInfo deserialization from the class methods to
the controller_util functions. These are the only usages of the
protobuf [de]serialization interface outside of tests.

BUG=b:265998356
TEST=./run_tests

Change-Id: I272807e611490289dd11103ee142a9984510aec5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4179354
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Lizzy Presland <zland@google.com>
Commit-Queue: Alex Klein <saklein@chromium.org>
diff --git a/api/controller/sysroot_unittest.py b/api/controller/sysroot_unittest.py
index 75f1c70..022587b 100644
--- a/api/controller/sysroot_unittest.py
+++ b/api/controller/sysroot_unittest.py
@@ -14,7 +14,6 @@
 from chromite.api.controller import sysroot as sysroot_controller
 from chromite.api.gen.chromite.api import sysroot_pb2
 from chromite.api.gen.chromiumos import common_pb2
-from chromite.lib import binpkg
 from chromite.lib import cros_build_lib
 from chromite.lib import cros_test_lib
 from chromite.lib import osutils
@@ -183,7 +182,7 @@
         rc_patch.assert_called_with(
             force=force,
             package_indexes=[
-                binpkg.PackageIndexInfo.from_protobuf(x)
+                controller_util.deserialize_package_index_info(x)
                 for x in package_indexes
             ],
             upgrade_chroot=upgrade_chroot,
@@ -840,7 +839,7 @@
             install_debug_symbols=True,
             packages=[],
             package_indexes=[
-                binpkg.PackageIndexInfo.from_protobuf(x)
+                controller_util.deserialize_package_index_info(x)
                 for x in package_indexes
             ],
             use_flags=[],