sched/critmon: Fix CPU load stats incorrect when using SCHED_CPULOAD_CRITMONITOR

[anchao]

Summary

sched/critmon: Fix CPU load stats incorrect when using SCHED_CPULOAD_CRITMONITOR

Fix the abnormal CPU usage statistics issue caused by missing update
of run_start timestamp in the target task (to) TCB when the CPU load
counting mode is SCHED_CPULOAD_CRITMONITOR.

Before this fix, the to->run_start was not set when switching context,
leading to incorrect CPU usage calculation (e.g., Idle_Task showed 52.9%
CPU usage instead of 100%, and running tasks had wrong non-zero values).
After fixing, the CPU statistics return to normal: Idle_Task correctly
shows 100% usage, and non-running tasks show 0% as expected.

Enable:

+CONFIG_SCHED_CPULOAD_CRITMONITOR=y
+CONFIG_SCHED_CRITMONITOR=y

Before:

nsh> ps
  TID   PID  PPID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK            STACK    CPU COMMAND
    0     0     0   0 FIFO     Kthread   - Ready              0000000000000000 0069584 52.9% Idle_Task
    1     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067456  0.0% sim_loop_wq 0x7b4417a003f0 0x7b4417a00470
    2     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067464 17.6% hpwork 0x4014dba0 0x4014dc20
    3     3     0 100 FIFO     Task      - Running            0000000000000000 0067496 36.8% nsh_main

After:

nsh> ps
  TID   PID  PPID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK            STACK    CPU COMMAND
    0     0     0   0 FIFO     Kthread   - Ready              0000000000000000 0069584 100.0% Idle_Task
    1     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067456  0.0% sim_loop_wq 0x7646932003f0 0x764693200470
    2     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067464  0.0% hpwork 0x4014dba0 0x4014dc20
    3     3     0 100 FIFO     Task      - Running            0000000000000000 0067496  0.0% nsh_main

This issue was introduced by PR #17075, where the run_start update for the
target task was omitted in the SCHED_CPULOAD_CRITMONITOR branch.

Signed-off-by: chao an anchao.archer@bytedance.com

Impact

N/A

Testing

sim/nsh,

Enable:

+CONFIG_SCHED_CPULOAD_CRITMONITOR=y
+CONFIG_SCHED_CRITMONITOR=y

Before:

nsh> ps
  TID   PID  PPID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK            STACK    CPU COMMAND
    0     0     0   0 FIFO     Kthread   - Ready              0000000000000000 0069584 52.9% Idle_Task
    1     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067456  0.0% sim_loop_wq 0x7b4417a003f0 0x7b4417a00470
    2     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067464 17.6% hpwork 0x4014dba0 0x4014dc20
    3     3     0 100 FIFO     Task      - Running            0000000000000000 0067496 36.8% nsh_main

After:

nsh> ps
  TID   PID  PPID PRI POLICY   TYPE    NPX STATE    EVENT     SIGMASK            STACK    CPU COMMAND
    0     0     0   0 FIFO     Kthread   - Ready              0000000000000000 0069584 100.0% Idle_Task
    1     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067456  0.0% sim_loop_wq 0x7646932003f0 0x764693200470
    2     0     0 224 FIFO     Kthread   - Waiting  Semaphore 0000000000000000 0067464  0.0% hpwork 0x4014dba0 0x4014dc20
    3     3     0 100 FIFO     Task      - Running            0000000000000000 0067496  0.0% nsh_main