Add support for reporting product components to Omaha.

Parse the product_components file from os-release.d and report
them in separate xml attributes.

Bug: 67872115
Test: check omaha request
Change-Id: I82cc3ef30b0cc9bab33f8e7eb939856a4740b9e3
(cherry picked from commit a025114f8df6509f80e60b19b5eca615610104b1)
diff --git a/omaha_request_params.h b/omaha_request_params.h
index ba7f2c3..73edd6f 100644
--- a/omaha_request_params.h
+++ b/omaha_request_params.h
@@ -130,6 +130,9 @@
   inline std::string system_version() const {
     return image_props_.system_version;
   }
+  inline std::string product_components() const {
+    return image_props_.product_components;
+  }
 
   inline std::string current_channel() const {
     return image_props_.current_channel;