New DSL implementation (#579)

The PR contains following changes:
Python side:
- Channel based DSL implementation: decouple channel with chunk.
- Users create channel explicitly, only need local_rank, remote_rank and
channel_type
- Adjust executor json file, add remote_buffer fields, different op can
use different channel and remote buffers combination.
- Reimplement operation fusion, data dependency check mechanism
- Add new op such as semaphore, pipeline 
- Clean code and enhance document
C++ side: 
- Support new execution file json format
- Support semaphore and pipeline operation
- code clean, support non-zero copy scenario

---------

Co-authored-by: Caio Rocha <caiorocha@microsoft.com>
Co-authored-by: Changho Hwang <changhohwang@microsoft.com>

python/test/executor_test.py

@@ -184,7 +184,7 @@ def main(
     npkit_dump_dir = env().npkit_dump_dir
     if npkit_dump_dir != "":
         npkit.init(mscclpp_group.my_rank)
-    execution_plan = ExecutionPlan(execution_plan_path)
+    execution_plan = ExecutionPlan(execution_plan_path, mscclpp_group.my_rank)
     collective = execution_plan.collective()
 
     dtype = parse_dtype(dtype_str)