FlowMatch schedulers - closing the gap

As stated [here](https://github.com/huggingface/diffusers/issues/9490#issuecomment-2369756363), lets close the scheduler gap!

Problem statement:
- Most (if not all quality ones) new models are DiT based
- Implementation of DiT based models in Diffusers typically requires Flow-match type schedulers
- Currently *only* working scheduler is `FlowMatchEulerDiscreteScheduler` which creates a massive gap!

(just for completeness, there is also an older implementation of `FlowMatchHeunDiscreteScheduler`, but its not updated to support required `set_timesteps` or `mu` inputs, so it cannot be used with newer DiT models like Flux.1)

on the other hand, ComfyUI allows use of any regular scheduler with DiT and does not require separate duplicate -FlowMatch variant of the same scheduler (e.g. *EulerDiscrete* vs *FlowMatchEulerDiscrete*) with Flux.1.

reference: matrix of different schedulers used with Flux.1.Dev via ComfyUI:

cc: @yiyixuxu @sayakpaul @DN6 @asomoza