samples: Add task statistics and semaphore samples

[Aditya-abs397]

Summary

Adds two new samples (samples/stats and samples/sem) demonstrating AstraRTOS's task statistics and the counting semaphore implementation for a resource with limited concurrent access.

What it does

Task statistics sample (samples/stats)

• Defines two tasks: stats_task (telemetry) and addition_task (a simple counter, included to give the stats output a second user task to report on).
• stats_task calls os_task_get_stats() once per second for every active task in the scheduler.
• Reports run count, stack high-water mark, and allocated stack size.
• Output includes both user-created tasks and the scheduler's auto-created idle task.
• Uses polled UART (uart_send_string) for printing.

Semaphore sample (samples/sem)

• Defines four tasks (task_a - task_d) across three priority levels.
• Shared resource protected by a counting semaphore initialized with capacity = 2.
• Each task waits, acquires, holds the resource for 300 ms, then releases in a loop.
• Demonstrates that os_sem_give() wakes the highest-priority waiting task first when a slot frees up.
• UART output is protected, so logs are clean and non-interleaved.

Testing

Verified both samples on QEMU

Semaphore sample output:

Task statistics sample output:

Related

Part of #15

[Aditya-abs397]

Worked on suggested changes.

[vedantmalkar]

pinging @mt-tass

[mt-tass]

@Aditya-abs397 did you test this on board ?

[Aditya-abs397]

@mt-tass I haven't tested it on board yet, will make sure to do it before tomorrow

[mt-tass]

@Aditya-abs397 updates ?

[Aditya-abs397]

@mt-tass Tested both samples on stm32 discovery board, its working

sem_basic testing

sem.implementation.mp4

stats_basic testing