Previously:
* applications were using isc_app as the base unit for running the
application and signal handling.
* networking was handled in the netmgr layer, which would start a
number of threads, each with a uv_loop event loop.
* task/event handling was done in the isc_task unit, which used
netmgr event loops to run the isc_event calls.
In this refactoring:
* the network manager now uses isc_loop instead of maintaining its
own worker threads and event loops.
* the taskmgr that manages isc_task instances now also uses isc_loopmgr,
and every isc_task runs on a specific isc_loop bound to the specific
thread.
* applications have been updated as necessary to use the new API.
* new ISC_LOOP_TEST macros have been added to enable unit tests to
run isc_loop event loops. unit tests have been updated to use this
where needed.
As we are going to use libuv outside of the netmgr, we need the shims to
be readily available for the rest of the codebase.
Move the "netmgr/uv-compat.h" to <isc/uv.h> and netmgr/uv-compat.c to
uv.c, and as a rule of thumb, the users of libuv should include
<isc/uv.h> instead of <uv.h> directly.
Additionally, merge netmgr/uverr2result.c into uv.c and rename the
single function from isc__nm_uverr2result() to isc_uverr2result().
Previously, there was a single per-socket write timer that would get
restarted for every new write. This turned out to be insufficient
because the other side could keep reseting the timer, and never reading
back the responses.
Change the single write timer to per-send timer which would in turn
reset the TCP connection on the first send timeout.
