Add 256 as possible option within block-size arg (#1279)

Bringing back option of 256 as possible block-size arg value, that has
been lost in some of the last rebases.

It has been first added via
#971

The options of arguments are now defined by unpacking predefined type
hints

![image](https://github.com/user-attachments/assets/f1c0429b-6449-44a5-b0e8-326f465590ab)

https://github.com/HabanaAI/vllm-fork/blob/habana_main/vllm/engine/arg_utils.py#L611

Author: ksmusz

vllm/config.py

@@ -1325,7 +1325,7 @@ def matryoshka_dimensions(self):
         return getattr(self.hf_config, "matryoshka_dimensions", None)
 
 
-BlockSize = Literal[1, 8, 16, 32, 64, 128]
+BlockSize = Literal[1, 8, 16, 32, 64, 128, 256]
 CacheDType = Literal["auto", "fp8", "fp8_e4m3", "fp8_e5m2", "fp8_inc"]
 PrefixCachingHashAlgo = Literal["builtin", "sha256"]