Deprecate posix timer

## Brief feature description

Deprecate posix timer from iceoryx code base.

## Detailed information

Posix timer has several issues (concurrency, truncation) and is pretty heavy weight and a bit slow. As iceorxy needs to be very responsive the posix timer should be removed and replaced with a lightweight stopwatch.

This will also close #190 as it'll be obsolete.

Tasks
- [x] create `DeadlineTimer` or similar and replace this part of the `PosixTimer` where applicable
- [x] create an object that creates a thread and peridically executes a task
- [ ] create a small wrapper around a `posix::semaphore` which can be used for `concurrent::PeriodicTask`
- [x] replace the keep alive message from a `std::chrono` timestamp with a `units::Duration` from a `timespec` initialized with `clock_gettime` with `CLOCK_REALTIME` -> maybe better to use a different issue for this