[IO] document and adjust tests to changes in io_uring's broken link handling

Closes #20

See merge request i4/manycore/emper!212

[io/tests] gracefully terminate the runtime on success

See merge request !213

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.

[Runtime] use pthread_getaffinity_np to determine default worker count

Closes #19

See merge request !211

The value reported by std::thread::hardware_concurrency() can be more
than the available CPUs to the current process for example if EMPER runs
in a container or qemu.
GNU nproc(1) does the right thing and we can take inspiration from them.
The solution is to use pthread_getaffinity_np which fills a CPU set with
all CPU a pthread can be scheduled on.
We use this more precise CPU count if possible.

[gitlab-ci] Bump flowdalic/debian-testing-dev to 1.12

See merge request !209

[Future] Fix clang-tidy issue in MadviseFuture

See merge request !208

[gitlab-ci] Bump debian-testing-dev image to 1.10

See merge request !199

[IO] add a madvise Future

See merge request i4/manycore/emper!206

Fix most llvm-12 clang-tidy warnings in IO code

See merge request i4/manycore/emper!205

Batch dequeue from AnywhereQueue

See merge request i4/manycore/emper!196

Thanks llvm 12 :)

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

Found during changing Future member types.

The posix versions (close/openat) return int as well.
And this fixes a narrowing conversion in c_emper.cpp: emper_openat and emper_close

Use int32_t as Future returnValue instead of ssize_t since
io_uring uses int32_t not ssize_t as results value therefore it is
pointless to use a bigger type.

This shrinks the future size and prevents useless and implementation defined
narrowing conversions from ssize_t to int32_t.

Use union for flags and offset.

Ignore int to pointer cast clang-tidy warning.

[Debug] maybe-uninitialized should be ignored for gcc >= 11.1.0

See merge request !204

[check-license] Do not pass --max-args to xargs

See merge request i4/manycore/emper!203

GCC 11.1 fixes

See merge request i4/manycore/emper!202

[CountingPrivateSemaphore] Fix assert

See merge request i4/manycore/emper!200

xargs: warning: options --max-args and --replace/-I/-i are mutually exclusive, ignoring previous --max-args value

gcc 11.1 on my arch system complains that the calls to free
does not match the allocator function new[].

As the code comment above the assert indicates, the atomic exchange
operation may either return nullptr or a valid Context pointer. And
this is what the assert() should assert. :)

Reported-by: Florian Fischer <florian.fl.fischer@fau.de>

[Common] Call abort() instead of exit() in die()

See merge request i4/manycore/emper!198

Calling abort() has multiple advantages. First, it better matches the
semantic of DIE(_MSG) as it signals an abnormal process termination,
whereas exit() is a normal process termination (even though
potentially with an error exit code). Secondly, abort() throws
SIGABRT, which in turn triggers a coredump, hence the program's state
can be inspected afterwards.

[LAWS/Fiber] Introduce the concept of Multi-Fiber

See merge request i4/manycore/emper!195

LAWS, and similar scheduling strategies, only need to perform
refcounting and atomic operations if the fiber was placed in multiple
ready-lists in the first place.

Already check if fiber is runnable in scheduliing subsystem

See merge request !197

Already check if the fiber is in-fact runnable in the scheduling
subsystem. This should not make a difference when WS scheduling is
used, but makes a difference when LAWS is used.

[meson] propagate set_affinity_on_block

See merge request !194