I could not identify the commit that changes this behavior but
it is reproducible on our bigboxes and my arch system.

* Document data races of a future's state.
* Get and set a Future's state only through methods. This helps to
  add possibly needed atomic operations.
* Use atomics to get/set cancel and prepare state in IO_SINGLE_URING vaiant
* Add more IO debug messages
* Use the BPS of Futures with callbacks similar to those of forgotten
  ones to signal their preparation. The preparation mark the
  last moment where the Future is used in EMPER and after that the memory
  can be dropped.
  ATTENTION: This means not that the used resources of the IO request
  can be dropped. The kernel may still use a supplied buffer for example.
* Fix Future chain cancellation in SubmitActor

Currently canceling Futures would never happen because we
issued the cancel request only with the pointer of the future.
This works more by coincidence than by design because
the PointerTags::Future tagged onto the submitted future pointer is 0.

This does not work for callbacks because they are tagged with a
PointerTags != 0 and they don't use their callback pointer rather
than the future pointer.

Fix this by exporting the tagging from IoContext::prepareFutureChain
into IoContext::createFutureTag and use this when submitting a cancel
sqe.

Warn the user that they have to manually take care of the memory safety
of the callback because we can not await the callback in Future::cancel.

Add a test case to CancelFutureTest.

This makes the test closer to our echoserver.

I suspect some test which scale whith the number of CPUs to timeout
mostly on jenkins2.
This patch reduces the load when logging is active and increases the
load when logging is off.
Therefore our test build with debugoptimized will do less and hopefully
only timeout when they actually hung and the release test will do
more.

While we do not have yet LLVM 13 in the gitlab-ci, I use it on my
systems. So fix the new warnings found with clang-tidy 13.

The chosen amounts of echos take on my 16 core ryzen system ~5seconds.
This should hopefully reduce CI timeout where we are not sure if they are
bugs or legit timeouts. Furthermore this should reduce the amount of logs
we write and have to store after each CI run.

Before 05dc56ed the two test cases testDiskAndNetwork, testIov
where combined in one function which was terminating the runtime after the client
closed its socketafter the test was done.
This was already broken before 05dc56ed but after the separation of the
two use cases the race between the Runtime terminating and the execution of
the last parts of the test-runner's alphaFiber became bigger.

When the Runtime terminates because the last worker running the testIoV
code has outstanding IO the test-runner's successSem is never notified.

* Use more emper io functions
* Split the separate test cases into two functions
* Use C++ arrays where sensible

The tests may fail when repeated because the listener may bind to fast
to the tcp tuple again. This is fixed by using SO_REUSEPORT instead of SO_REUSEADDR.

TIL: SO_REUSEADDR is about address wildcards and SO_REUSEPORT allows
binding to the same tcp tuple.
https://stackoverflow.com/questions/14388706/how-do-so-reuseaddr-and-so-reuseport-differ

Add a generic way to specify socket options when creating a listen socket
with tcp_listener.

This allows use to remove the current hack that the test are always
build without NDEBUG regardless of the meson buildtype.

Which is fact fixes the failing io tests in release builds.
Because Future.hpp and Future.cpp see the same version of NDEBUG.

This allows the examination of stats which get printed in the Runtime
destructor.
Also remove useless stdlib includes (Why does iwyu not catch those?).

Until kernel commit cf10960426515 io_uring submitted sqe until it encountered
an invalid one. Now io_uring will catch the error on subimssion and
will cancel all sqe's contained in the link prior to the invalid one.

errno was never set on error and thus the DIE_MSG_ERRNO did not properly
report what happened.

Found during changing Future member types.

* Improve warn message in Future::cancel()
* Don't cancel a Future in the destructor if it was already cancelled or received
* Restructure CancelFutureTest into single separate test cases

With this I can not reproduce the weird CancelFutureTest behavior anymore
neither SIGABRT nor the timeout.

Move io and lib related tests into io/ and lib/.

Our test dictionaries not must have a 'source' key with an array
created with files().
This ensures we use always correct paths regardless of the actual directory
we are currently in.

Until https://github.com/mesonbuild/meson/issues/8608 is not solved
we have to separately specify the tests name in a 'name' key.