Review feedback: DAP thread IDs are scoped per client session, so deduping
the tree-wide thread list by (id, name) collapsed distinct threads that
different children happen to share — e.g. multiple identical worker scripts
each exposing { id: 1, name: "worker.js" }. Key the dedupe set by the owning
session id + thread id instead, so every live thread is preserved and only an
exact repeat within a single session's response is dropped.
Fixes#6663
roboomp
80df85a84b