ART: Take classloader into account for AttachAgent

Take a classloader into account for attaching an agent, if given.
This will use the library path from the classloader to find the
agent library.

Switch to libnativeloader to do the actual loading.

Bug: 70901841
Test: m test-art-host
Change-Id: I59ec55178792bc738fb06e0299522e207dd4a784
diff --git a/adbconnection/adbconnection.cc b/adbconnection/adbconnection.cc
index 2a9982a..a5c885a 100644
--- a/adbconnection/adbconnection.cc
+++ b/adbconnection/adbconnection.cc
@@ -583,7 +583,9 @@
           DCHECK(!agent_listening_);
           // Load the agent now!
           self->AssertNoPendingException();
-          art::Runtime::Current()->AttachAgent(MakeAgentArg());
+          art::Runtime::Current()->AttachAgent(/* JNIEnv* */ nullptr,
+                                               MakeAgentArg(),
+                                               /* classloader */ nullptr);
           if (self->IsExceptionPending()) {
             LOG(ERROR) << "Failed to load agent " << agent_name_;
             art::ScopedObjectAccess soa(self);