This adds support for POST in both h1 and h2 queues / stream binding.
The previous queueing tried to keep the "leader" wsi who made the
actual connection around and have it act on the transaction queue
tail if it had done its own thing.
This refactors it so instead, who is the "leader" moves down the
queue and the queued guys inherit the fd, SSL * and queue from the
old leader as they take over.
This lets them operate in their own wsi identity directly and gets
rid of all the "effective wsi" checks, which was applied incompletely
and getting out of hand considering the separate lws_mux checks for
h2 and other muxed protocols alongside it.
This change also allows one wsi at a time to own the transaction for
POST. --post is added as an option to lws-minimal-http-client-multi
and 6 extra selftests with POST on h1/h2, pipelined or not and
staggered or not are added to the CI.
wsi timeout, wsi hrtimer, sequencer timeout and vh-protocol timer
all now participate on a single sorted us list.
The whole idea of polling wakes is thrown out, poll waits ignore the
timeout field and always use infinite timeouts.
Introduce a public api that can schedule its own callback from the event
loop with us resolution (usually ms is all the platform can do).
Upgrade timeouts and sequencer timeouts to also be able to use us resolution.
Introduce a prepared fakewsi in the pt, so we don't have to allocate
one on the heap when we need it.
Directly handle vh-protocol timer if LWS_MAX_SMP == 1
lws_dll2 removes the downsides of lws_dll and adds new features like a
running member count and explicit owner type... it's cleaner and more
robust (eg, nodes know their owner, so they can casually switch between
list owners and remove themselves without the code knowing the owner).
This deprecates lws_dll, but since it's public it allows it to continue
to be built for 4.0 release if you give cmake LWS_WITH_DEPRECATED_LWS_DLL.
All remaining internal users of lws_dll are migrated to lws_dll2.
