Support page first layout zero copy for mooncake store (#8651)

Co-authored-by: Zhiqiang Xie <xiezhq@stanford.edu>

python/sglang/srt/server_args.py

@@ -575,6 +575,11 @@ class ServerArgs:
                 "Pipeline parallelism is incompatible with overlap schedule."
             )
 
+        if self.hicache_storage_backend == "mooncake":
+            # to use mooncake storage backend, the following conditions must be met:
+            self.hicache_io_backend = "kernel"
+            self.hicache_mem_layout = "page_first"
+
         # Speculative Decoding
         if self.speculative_algorithm == "NEXTN":
             # NEXTN shares the same implementation of EAGLE