sched/deadline: Convert schedtool example to chrt

 of the command line options. Please refer to rt-app documentation for more

 details (`<rt-app-sources>/doc/*.json`).

 The second testing application is a modification of schedtool, called

 schedtool-dl, which can be used to setup SCHED_DEADLINE parameters for a

 certain pid/application. schedtool-dl is available at:

 https://github.com/scheduler-tools/schedtool-dl.git.

 The second testing application is done using chrt which has support

 for SCHED_DEADLINE.

 The usage is straightforward::

  # schedtool -E -t 10000000:100000000 -e ./my_cpuhog_app

  # chrt -d -T 10000000 -D 100000000 0 ./my_cpuhog_app

 With this, my_cpuhog_app is put to run inside a SCHED_DEADLINE reservation

 of 10ms every 100ms (note that parameters are expressed in microseconds).

 You can also use schedtool to create a reservation for an already running

 of 10ms every 100ms (note that parameters are expressed in nanoseconds).

 You can also use chrt to create a reservation for an already running

 application, given that you know its pid::

  # schedtool -E -t 10000000:100000000 my_app_pid

  # chrt -d -T 10000000 -D 100000000 -p 0 my_app_pid

Appendix B. Minimal main()

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