key_value_store: pull LoadKeyValueFile into a module

This isn't used too often, so lets pull it out into a standalone
module.  It also has no real deps on other bits, so move it to
the utils namespaces.

BUG=chromium:997354
TEST=`./run_tests` passes

Change-Id: Ieee6b3476600cca98aaad7597cda57b6a79f3d55
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1790373
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_sdk.py b/scripts/cros_sdk.py
index 715ca0a..ca4e53d 100644
--- a/scripts/cros_sdk.py
+++ b/scripts/cros_sdk.py
@@ -38,6 +38,8 @@
 from chromite.lib import process_util
 from chromite.lib import retry_util
 from chromite.lib import toolchain
+from chromite.utils import key_value_store
+
 
 cros_build_lib.STRICT_SUDO = True
 
@@ -847,7 +849,7 @@
 
 
 def main(argv):
-  conf = cros_build_lib.LoadKeyValueFile(
+  conf = key_value_store.LoadFile(
       os.path.join(constants.SOURCE_ROOT, constants.SDK_VERSION_FILE),
       ignore_missing=True)
   sdk_latest_version = conf.get('SDK_LATEST_VERSION', '<unknown>')