Feat: ensure correct process termination in ingress/egress tracker (#…

…4101)

* refactor: move most of btc into separate module (no new changes)

* chore: tests submodule

(allows collapsing all tests when not needed)

* refactor: move the rest of btc into separate module (with a few changes)

* chore: remove stale comment

* feat: ensure correct process termination (using task_scope)

* chore: fix clippy

* chore: address review