this rolls up numerous changes that have been applied to the
main branch, including moving isc_task operations into the
netmgr event loops, and other general stabilization.
Previously, the taskmgr, timermgr and socketmgr had a constructor
variant, that would create the mgr on top of existing appctx. This was
no longer true and isc_<*>mgr was just calling isc_<*>mgr_create()
directly without any extra code.
This commit just cleans up the extra function.
(cherry picked from commit 3388ef36b3)
"resolve" is used by the resolver system tests, and I'm not
certain whether delv exercises the same code, so rather than
remove it, I moved it to bin/tests/system.
(cherry picked from commit d0ec7d1f33)