Merge mscclpp-lang to mscclpp project (#442)

First step to merge msccl-tools into mscclpp repo. In this step will
move all msccl related code, pass the current tests and do some
necessary refactor.

Add `mscclpp.language` module
Add `_InstructionOptimizer` and `DagOptimizer` class to optimize the dag
Add `DagLower` to lower dag to intermediate representation 
Add documents for mscclpp.language
Remove msccl related code

.github/workflows/mscclpp-lang.yml

@@ -0,0 +1,46 @@
+name: MSCCLPPLang
+
+on:
+  pull_request:
+    branches:
+      - main
+      - release/*
+
+jobs:
+  compare-diffs:
+    runs-on: 'ubuntu-latest'
+    container:
+      image: ghcr.io/microsoft/mscclpp/mscclpp:base-dev-${{ matrix.version }}
+
+    strategy:
+        fail-fast: false
+        matrix:
+          version: [ 'cuda11.8', 'cuda12.2' ]
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install mscclpp
+      run: |
+        CMAKE_ARGS="-DMSCCLPP_BYPASS_GPU_CHECK=ON -DMSCCLPP_USE_CUDA=ON" pip3 install .
+
+    - name: Copy test script/config to temp directory
+      run: |
+        cp python/test/test_generate_mscclpp_lang_result.py $RUNNER_TEMP/
+        cp python/test/configs/mscclpp_lang_test_config.json $RUNNER_TEMP/
+    - name: generate outputs
+      run: |
+        python3 $RUNNER_TEMP/test_generate_mscclpp_lang_result.py python/examples/ $RUNNER_TEMP/mscclpp_lang_test_config.json $RUNNER_TEMP/tests/pr-outputs/
+    - name: Checkout main branch
+      uses: actions/checkout@v4
+      if: github.event_name == 'pull_request' || github.event_name == 'push'
+      with:
+        ref: main
+    - name: Install msccl and dependencies
+      run: |
+        CMAKE_ARGS="-DMSCCLPP_BYPASS_GPU_CHECK=ON -DMSCCLPP_USE_CUDA=ON" pip3 install .
+    - name: generate outputs
+      run: |
+        python3 $RUNNER_TEMP/test_generate_mscclpp_lang_result.py python/examples/ $RUNNER_TEMP/mscclpp_lang_test_config.json $RUNNER_TEMP/tests/main-outputs/
+    - name: Compare outputs
+      run: |
+        diff -rw $RUNNER_TEMP/tests/main-outputs/ $RUNNER_TEMP/tests/pr-outputs/