api: Drop controller_util.PackageInfoToCpv.

Convert remaining usages of PackageInfoToCpv to
deserialize_package_info to allow dropping the SplitCPV usage.

BUG=b:187792048
TEST=run_tests, CQ

Change-Id: I90f48ce1d728bc077dbb6dac1807cb4468f0a8f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4548373
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Auto-Submit: Alex Klein <saklein@chromium.org>
diff --git a/api/controller/sysroot.py b/api/controller/sysroot.py
index d6ad97d..5a9ba36 100644
--- a/api/controller/sysroot.py
+++ b/api/controller/sysroot.py
@@ -335,7 +335,8 @@
     # Get the package atom for each specified package. The field is optional, so
     # error only when we cannot parse an atom for each of the given packages.
     packages = [
-        controller_util.PackageInfoToCPV(x).cp for x in input_proto.packages
+        controller_util.deserialize_package_info(x).atom
+        for x in input_proto.packages
     ]
 
     package_indexes = [