{bp-19972} sched/sporadic: fix policy switch and cross-task setparam

[jerpelea]

Summary

This PR fixes two bugs in the SCHED_SPORADIC handling of the scheduler, both found while testing sporadic policy switching:

sched_setscheduler(): The policy flag bits were cleared before the switch (policy) statement. Since TCB_FLAG_SCHED_FIFO is 0, the checks for "was the task previously SCHED_SPORADIC" inside the SCHED_FIFO/SCHED_RR cases could never be true. As a result nxsched_stop_sporadic() was never called when a sporadic task switched to another policy, leaking the sporadic state and its replenishment timers; a sporadic-to-sporadic reconfiguration ran nxsched_initialize_sporadic() instead of reset, leaking the old state. The flags are now cleared only after the previous policy has been evaluated.

sched_setparam(): set_sporadic_param() tested rtcb (the calling task) instead of tcb (the task being modified). A cross-task sched_setparam() therefore never updated the target's sporadic parameters, and if the caller was itself sporadic while the target was not, it would reset a task with no sporadic state (NULL-pointer / assertion failure) and write parameters into the caller's own sporadic state.

Impact

RELEASE

Testing

CI

[jerpelea]

CI fix
apache/nuttx-apps#3775