Ysc pluggable scheduler

[yannicks1]

This PR moves the (spyre specific) scheduler class into the plugin repo vllm-spyre.
it goes along with this ->PR<- in the vllm-spyre repository

Changes:

• vllm/config.py: introducing new variable scheduler_cls for class SchedulerConfig (can be a path (str) or a class directly) and removing spyre specific code to 'load warmup shapes and sort by "speed"' (moved to vllm-spyre)
• vllm/engine/llm_engine.py: importing Scheduler based on vllm_config.scheduler_config.scheduler_cls
• vllm/core/scheduler.py: removing all spyre specific code from the scheduler logic
• vllm/envs.py: removing all spyre related env variables (moved to vllm-spyre)
• remove the variable: SchedulerConfig.spyre_warmup_shapes in vllm/vllm.config.py

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[sducouedic]

LGTM

[sducouedic]

I also think it is better with Scheduler (with capital letter), but I've seen elsewhere in the code that they used cls
for example when retrieving the worker class:

cls = resolve_obj_by_qualname(target_worker_config.parallel_config.worker_cls)
target_worker = cls(*args, **kwargs)