feat: update MetaX examples with improved API usage

Updated examples:
- metax_example.cpp: Simplified device info, cleaner profiling flow
- metax_benchmark.cpp: Memory bandwidth and profiling overhead tests
- metax_profiling.py: Python profiling example with PyTorch support

Changes:
- Use mcGetDeviceProperties for device info retrieval
- Add profiling overhead measurement in benchmark
- Support both PyTorch and native MACA profiling modes

Author: chenxingqiang