libperfmgr: change to use Value directly in config

Using Value directly is more clear and intuitive than using an index of
Values.

Bug: 77282526
Test: libperfmgr_test and boot wahoo

(cherry picked from commit 4ea001c2d3dc3f5c8421a5e86098272b295b213e)

Change-Id: Id6bd284c431d347e36ba8ce2bb4c82a7a4924852
diff --git a/libperfmgr/include/perfmgr/Node.h b/libperfmgr/include/perfmgr/Node.h
index f31b012..ea4c3e3 100644
--- a/libperfmgr/include/perfmgr/Node.h
+++ b/libperfmgr/include/perfmgr/Node.h
@@ -42,8 +42,8 @@
 // value. For each value, there may be multiple requests because different
 // powerhints may request the same value, and the requests may have different
 // expiration times. All of the in-progress powerhints for a given value are
-// collected in a RequestGroup. Node class is not thread safe so it need protection
-// from caller e.g. NodeLooperThread.
+// collected in a RequestGroup. Node class is not thread safe so it needs
+// protection from caller e.g. NodeLooperThread.
 class Node {
   public:
     Node(std::string name, std::string node_path,