Reconcile protobuf package names with paths

* Makes the import paths reflect the package namespaces.
  * This matters especially for import of protos defined here into
    infra/proto, as it avoids conflicts with paths local to infra/proto.

Various clients are affected in following ways:
* Protobuf:
  * import paths change from "api/*" -> "chromiumos/config/api/*"
  * package names unchanged
* Go: Unchanged
* Starlark:
  * protobuf load paths changed from "api/*" ->
    "chromiumos/config/api/*"
* Python:
  * In payload_utils: Via payload_utils/chromiumos, imports change
    import config.* -> import chromiumos.config.*
  * Inside Chrome OS SDK: The bindings are installed as a python package
    import config.* -> import chromiumos.config.*
* Recipe: import config.* -> import chromiumos.config.*

BUG=chromium:1069877
TEST=CQ


Change-Id: I158b3f4f4479058754ffcfd8c7e8eb85746b3d67
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/config/+/2144905
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Commit-Queue: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Andrew Lamb <andrewlamb@chromium.org>
diff --git a/payload_utils/checker/io_utils.py b/payload_utils/checker/io_utils.py
index 8530509..4fb4981 100644
--- a/payload_utils/checker/io_utils.py
+++ b/payload_utils/checker/io_utils.py
@@ -5,7 +5,7 @@
 
 import os
 
-from config.payload import config_bundle_pb2
+from chromiumos.config.payload import config_bundle_pb2
 
 
 def read_config(path: str) -> config_bundle_pb2.ConfigBundle: