[Core] Deprecating block manager v1 and make block manager v2 default (#8704)

Removing the block manager v1. This is the initial piece of prefix-caching-centric design. In order to achieve prefix-caching-centric design, we need to simplify the code path so that we only use v2 block manager (which has much higher performance on prefix caching).

tests/spec_decode/e2e/test_integration_dist_tp4.py

@@ -19,9 +19,6 @@ SPEC_MODEL = "JackFram/llama-68m"
     [[
         # Skip cuda graph recording for fast test.
         "--enforce_eager",
-
-        # Required for spec decode.
-        "--use-v2-block-manager",
         "--tensor-parallel-size",
         "4",
     ]])
@@ -71,9 +68,6 @@ def test_draft_model_tp_lt_target_model_tp4(common_llm_kwargs,
 
         # Skip cuda graph recording for fast test.
         "--enforce-eager",
-
-        # Required for spec decode.
-        "--use-v2-block-manager",
         "--tensor-parallel-size",
         "4",
     ]])