[dynamic control] Add policy pipeline initializing manager (open-telemetry#2826)

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: jackshirazi

dynamic-control/src/main/java/io/opentelemetry/contrib/dynamic/policy/OpampPolicyProvider.java

@@ -337,7 +337,8 @@ static Duration getGlobalPollingIntervalForTest() {
   }
 
   /** Resets shared provider test state, including polling interval and active provider tracking. */
-  static void resetForTest() {
+  // TODO: refactor/rescope to make this not public at some point
+  public static void resetForTest() {
     setGlobalPollingInterval(DEFAULT_POLLING_INTERVAL);
     ACTIVE_PROVIDERS.clear();
   }