Revert "Revert "ART: Ensure plugin is loaded on AttachAgent""

Agents require the JVMTI plugin. Ensure that it is loaded when
trying to satisfy an AttachAgent request. Amend test 909.

This reverts commit 98cf7cf8.
Blacklist debuggable test configurations for negative test.

Bug: 31682382
Test: m test-art-host-run-test-909-attach-agent
Change-Id: I7720a18689bd6ddee38292dd42faf190fc06d14d