Added call_scheduler

[limonspb]

allows to shcedule any function for a call like that, for example:

#include "common/call_scheduler.h"
....
ScheduleCall(myFunction, 5000000); // 5 seconds

myFunction will be executed by scheduler after 5 seconds or more.
Keep in mind that the execution time is not accurate, task running at 1000hz with TASK_PRIORITY_MEDIUM.

Adds new debug:

    DEBUG_SET(DEBUG_CALL_SCHEDULER, 0, lrintf(scheduledCallsCount));
    DEBUG_SET(DEBUG_CALL_SCHEDULER, 1, lrintf(refusedCalls));
    DEBUG_SET(DEBUG_CALL_SCHEDULER, 2, lrintf(totalCalls));

new functionality could be helpful in many cases, for example:
While saving stats/settings, can check if quad is stable (on the ground) then save, otherwize reschedule saving.
In future OSD menus when need to perform gyro-readings for some period of time.

[github-actions]

Do you want to test this code? You can flash it directly from Betaflight Configurator:

• Simply put #13636 (this pull request number) in the Select commit field of the Configurator firmware flasher tab (you need to Enable expert mode, Show release candidates and Development).

WARNING: It may be unstable. Use only for testing!

[limonspb]

lol, just found out there is already similar functionality "dispatchAdd" :)
Closing this @haslinghuis

[SteveCEvans]

See https://github.com/betaflight/betaflight/blob/master/src/main/fc/dispatch.c which does this.