Add mcp_streamable route and refactor some common code between sse and streamable. Update tests for 400 errors in sse.

.github/workflows/tests_ci.yml

@@ -21,7 +21,7 @@ jobs:
       - name: Set Up Python
         uses: actions/setup-python@v4
         with:
-          python-version: "3.10"
+          python-version: "3.11"
 
       - name: Install Dependencies
         run: |