[Core] Scheduling optimization 2

[rkooo567]

This PR adds 2 optimization

I found the main overhead is coming from get_max_num_running_seqs because it needs to create a list of sequences.

This adds 2 optimizations

1. If status is None, get_num_seqs doesn't have to create a list.
2. If we already know num_seqs token budget is updated before calling schedule_Running, we allow to skip it from schedule_running. This will skip get_max_num_running_seqs so it improves perf

Before this PR, each iteration on A10 takes 2.67ms (the original scheduler logic takes about 2ms). After 1, it became 2.32.4 ms. After 2, it becomes 2~2.1ms

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[rkooo567]

ignore this func

[simon-mo]

LGTM given we just re-use the enable_chunking flag and removing the `before_regression_

[rkooo567]

this commit: Throughput: 24.59 requests/s, 12587.93 tokens/s
before regression: Throughput: 24.92 requests/s, 12757.61 tokens/s
before this commit: Throughput: 24.23 requests/s, 12404.63 tokens/s

So less than 2% diff from before regression after this commit

[rkooo567]

Throughput: 24.80 requests/s, 12699.84 tokens/s

lol I added if opposite when I removed the flag and replaced it to enable_chunk

After fixing this, the perf seems almost identical to before regrssion @simon-mo