enable flux pipeline compatible with unipc and dpm-solver (#11908)
* Update pipeline_flux.py
have flux pipeline work with unipc/dpm schedulers
* clean code
* Update scheduling_dpmsolver_multistep.py
* Update scheduling_unipc_multistep.py
* Update pipeline_flux.py
* Update scheduling_deis_multistep.py
* Update scheduling_dpmsolver_singlestep.py
* Apply style fixes
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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: Álvaro Somoza <asomoza@users.noreply.github.com>