fix(simulation): clamp simulated FIFO accel/gyro samples to int16 range

[farhangnaderi]

Fixes #23469.

The simulated FIFO emulation in SimulatorMavlink::update_sensors() converts SI sensor values to raw counts and assigns them to the int16 sample fields of sensor_accel_fifo / sensor_gyro_fifo. Beyond the emulated full-scale range (16 g for accel 0, 2000 °/s ≈ 34.9 rad/s for gyro 0) the float-to-int16 conversion overflows and wraps, so a fast-spinning vehicle (e.g. the monocopter at ~50 rad/s) sees its gyro data flip sign instead of saturating — the "inverted gyro at fast rates" reported in the issue.

This change constrains the raw counts to [INT16_MIN, INT16_MAX] before the assignment, for both the accel and gyro FIFO paths, so out-of-range values saturate at full scale. Since PX4Accelerometer/PX4Gyroscope already flag FIFO samples at the int16 rails as clipped, the saturation is now correctly reported as clipping to downstream consumers (EKF2, vibration metrics), matching real IMU behavior and the expected behavior described in the issue.

Tested by building px4_sitl_default; the change is limited to the SITL MAVLink simulator sensor path and does not affect hardware targets.

---

[farhangnaderi]

I have not tested this. Fable did. I will test it later myself.