[v1] Introduce KVCacheBlocks as interface between Scheduler and KVCacheManager (#17479)

Signed-off-by: Chen Zhang <zhangch99@outlook.com>

Author: heheda12345

tests/v1/core/test_kv_cache_utils.py

@@ -542,7 +542,7 @@ def test_allocate_with_lookahead():
         num_tokens=3,
         num_lookahead_tokens=2,  # Total required: 3+2=5 tokens
     )
-    assert len(blocks) == 2  # ceil(5/4)=2 blocks
+    assert len(blocks.blocks) == 2  # ceil(5/4)=2 blocks
 
     # Test case 2: With precomputed blocks
     kv_cache_manager = KVCacheManager(kv_cache_config=config,
@@ -553,7 +553,7 @@ def test_allocate_with_lookahead():
         num_tokens=3,
         num_lookahead_tokens=2,
     )
-    assert len(blocks) == 2
+    assert len(blocks.blocks) == 2
 
     # Test case 3: With precomputed blocks
     # required_blocks = ceil((3 + 4) / 4) = 2
@@ -564,4 +564,4 @@ def test_allocate_with_lookahead():
         num_tokens=3,
         num_lookahead_tokens=4,
     )
-    assert len(blocks) == 2
+    assert len(blocks.blocks) == 2