[IO] provide memory to store continuation Fiber* by the caller

See merge request !180

Reason for this change is that we suspect the dynamic memory allocation
in reapCompletions for the return vector to be rather costly.

We know the maximum amount of memory needed to store continuation Fiber*
at compile-time because the size of the CQs is fixed.
This allows us to pass a buffer big enough to store all possible continuation
Fiber* to reapCompletions from the caller preventing the need for
the dynamic memory allocation for the returned vector.
The caller has to ensure that the memory is free of data races.
Currently this is ensured by allocating the buffer on the stack.

[io/Stats] do not try to print the globalIo stats if there are none

See merge request !178

[io] do not reap completions after resubmitting a PartialCompletableFuture

Closes #17

See merge request !177

Reaping completions after resubmitting a PartialCompletableFuture
can lead to unbound recursion when the resubmitted Future was
again partially completed during the resubmission.

We already observed a stack overflow due to recursion for this in
the IncrementalCompletionTest using completer thread with wakeup
behaviour.

[EchoServer] fix echo function

See merge request !176

The break was not in the right scope and thus exiting the echo loop
immediately in the first iteration.

[EchoServer] exit the echo server by terminate the runtime

See merge request !175

Since stats are printed in the Runtime destructor we can not simply call
exit() and have to properly terminate the Runtime.
When the echo server receives a "quit" message all active connections will
return and the Runtime will terminate if there is no work left.

introduce new CRTP based worker sleep algorithm abstraction

See merge request !172

Introduce AbstractWorkerSleepStrategy a CRTP interface class for a worker
sleep algorithm.
A concrete WorkerSleepStrategy must implement the following functions:

	template <CallerEnvironment callerEnvironment>
	void notifyMany(unsigned count);

	template <CallerEnvironment callerEnvironment>
	void notifyOne();

	template <CallerEnvironment callerEnvironment>
	void notifyAll();

	void notifySpecific(workerid_t workerId);

	void sleep();

The runtime uses this interface to notify the workers about new work
as well as ensuring that all workers get notified on termination.

All sempahore based worker sleep algorithm code was moved from the Runtime
into SemaphoreWorkerSleepStrategy which takes the used Semaphore as a
template parameter.

This interface should be an zero-cost abstraction.

Encapsulating the worker sleep algorithm behind an interface allows us
to easier experiment with different approaches not based on semaphores
("Wait in the io_uring", "Empty flag per WSQ").

Implement a generic notifySpecific algorithm for SemaphoreWorkerSleepStrategy.
This algorithm comes with runtime overhead and is only used when it is
used by the runtime and the semaphore implementation does not provide a
own implementation.

[EchoClient] support latency histograms

See merge request !174

Histograms can only be collected when using a fixed amount of iterations.

When the '--histogram <file>' argument is passed each Client
collects 4 time stamps (each 8 byte):

1. Before requesting the send operation
2. After requesting the send operation
3. After getting unblocked and dispatched because the send operation finished
4. After getting unblocked and dispatched because the recv operation finished

Taking the timestamps is enabled using a template and thus does not introduce
any runtime cost if they are not used except binary size.

Before termination three latencies are calculated and written to the histogram
file as csv data for each client and each echo.

1. total_latency := (T4 - T1)
2. after_send_latency := (T4 - T2)
3. after_send_dispatch_latency := (T4 - T3)

[repare-build-dir] Check for unknown meson options

See merge request i4/manycore/emper!173

Meson does only emit a warning if unknown options are passed. In our
case, this is always something we should take care of, because an
option we assumed we configured, had no effect.

See also https://github.com/mesonbuild/meson/pull/8658

[EchClient] calculate and output experiment totals

See merge request !171

This makes looking at individual experiment results and identifying
outliers easier.

[EchoClient] overhaul the EchoClient.cpp

See merge request i4/manycore/emper!165

Split output between two ini sections: global, clients.
The global section includes results like:
Arguments, total time spent in each phase, ...

The clients section contains a sigle key 'csv' containing the csv data
from each client inclufing the header:
iterations, latency, reconnects, unexpected echos

This leaves the post processing of the data to another program
and does not hide experiment behavior (e.g. starvation of single
clients) behind averages.

Remove support for appending to an output file, because we do not
use it in our emper-io-evaluation and it does not work anymore with the
new output format.

[Future] improve cancellation

Closes #16

See merge request !170

* Unconditionally reconnect when the TCP connection was reset and count the reconnects
* Send Client id and iteration in each echo
* Use a Client class holding a clients state instead of a pthread style clientFunc
* Create the Client object in the client Fiber to use NUMA first-touch policy
* Reduce code duplication:
  * starting a new Client is now done with Client::startNew
  * latency measurement and error handling are moved from the clientIteration*
    functions in the Client::run function

* 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.

Add WorkerLocalData and use it for stats

See merge request !158

For some reason, my IWYU wants this include to be removed.

Minor fixes

See merge request !169

[LawsScheduler] Delete stray #define EMPER_OVERFLOW_QUEUE

See merge request !168

[check-iwyu] Do not fail right away if IWYU_TOOL fails

See merge request !167

Since only newer versions of IWYU_TOOL fail with an exit code, we have
to disable -e around the IWYU_TOOL invocation. Otherwise we would not
print IWYU_LOG.

[gitlab-ci] Update flowdalic/debian-testing-dev to 1.8

See merge request !162

[iwyu] Take load average into consideration on CI

See merge request !151

[IO] fix IoCompleterBehavior::none

See merge request !161