flow matching lcm scheduler (#11170)

* add flow matching lcm scheduler
* stochastic sampling
* upscaling for scale-wise generation

* Apply style fixes

* Apply suggestions from code review

Co-authored-by: hlky <hlky@hlky.ac>

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: hlky <hlky@hlky.ac>

Author: 4 people