[IoContext] Remove duplicate CQE_BATCH_COUNT delcaration and definition

See merge request i4/manycore/emper!233

[IO] Implement configurable "simple architecture"

See merge request i4/manycore/emper!230

Introduce a new meson option io_single_uring which causes EMPER
to only use the GlobalIoContexts for all IO.

To submit SQEs to the io_uring SQ SubmitActor is used.

Futures can be in a new state where they are submitted to the SubmitActor
but not to the io_uring yet.
In this state isSubmitted && !isPrepared th Future must not be destroyed
to ensure this we yield when forgetting a Future until it is prepared
and thus it is safe to destroy it.

This commit contains no optimizations (no batching, no try non blocking
syscall first, ...)

Refacter GlobalIoContext.cpp:

* rename globalCompleter to completer
* make the completer loop non-static

Move all definitions from emper.hpp in compilation unit

See merge request i4/manycore/emper!232

Move emper::sleep() implemention from header in compilation unit

See merge request !231

[AbstractWorkStealingScheduler] Get rid of "rand() % workerCount"

See merge request i4/manycore/emper!229

The "rand() % workerCount" constructed used in the work-stealing
scheduler is flawed. It has a bias toward lower worker IDs due the
modulo operation. This is something I always wanted to get rid of, but
never found the time to do it. Until know.

Get rid of it and replace it with
std::uniform_int_distribution<workerid_t> (as field the Worker
instance).

The main changes in AbstractWorkStealingScheduler are
- use currentWorker->nextRandomWorkerId() (instead of the flawed construct)
- currentWorker->getWorkerId() (instead of Runtime::getWorkerId())

[stats] blocked contexts

See merge request !224

Support distributing multiple echoclient over the network

See merge request !228

The Coordinator is used for our echo evaluation and implements
a barrier style synchronization mechanism for processes spread across the network.

[meson] allow building EMPER on systems whithout <filesystem>

See merge request !221

Add meson option for "check anywhere queue while stealing"

See merge request !207

[io.hpp] add blocking functions using timeouts

See merge request !226

[stats] Add max-queue-length stats to AbstractWorkStealingScheduler

See merge request !223

[echoclient] print a short description of parameters

See merge request !225

Add docker tooling

See merge request i4/manycore/emper!219

Check if std::filesystem::recursive_directory_iterator and std::filesystem::path
are available before using those in EMPER code.

We do not export the symbols using the not supported filesystem features
in our public headers using preprocessor ifdef.

But the code in the cpp files using it not removed using the preprocessor.
To allow linkage we use a constexpr which throws a logic_error on runtime
rendering the rest of the code dead und thus prevents its generation by
the compiler.
This methods allows the compiler to see the code in its analysis passes
but does not fail during linking.

Allow meson.build files in emper/ subdirectories add configuration options
by consuming the conf_data object after all subdirectories were visited.

Introduce a quasi naming standard for cpp feature flags in meson code:
	cpp_has_<namespace>_<feature>

Examples:
	cpp_has_fs_path

Usage run "docker.sh <your command>" to execute <your command> in the
docker image extracted from .gitlab-ci.yml in the emper root directory

NOTE: seccomp filtering is disabled for now since io_uring_* syscalls
are not working everywhere as expected.

[fsearch] gracefully terminate the runtime to print the collected stats

See merge request i4/manycore/emper!222

[PipeSleepStrategy] use C++ smart ptrs instead of manual memory management

See merge request i4/manycore/emper!220

The destructor of PipeSleepStrategy caused segmentation faults when
running optimized. Because the stats pointer is not initialized it was
possibly to pass a garbage pointer to delete. Now we use a well defined
C++ smart pointer which fixes the problem and is more idiomatic anyway.

[IoContext] wrap CQ locking in if constexpr

See merge request i4/manycore/emper!218

We don't need to pay the overhead of the atomic operations on each
dispatch loop if there is no concurrent access to worker CQs.