fix: support mcp env vars and nested inputs (#7772)

* env vars for mcp

* support nested mcp schemas

* [autofix.ci] apply automated fixes

* Update mcp_component.py

* [autofix.ci] apply automated fixes

* Update mcp_component.py

* Update mcp_component.py

* fix lint and mypy

* fix tests

---------

Co-authored-by: Edwin Jose <edwin.jose@datastax.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

src/backend/tests/unit/components/tools/test_mcp_component.py

@@ -82,6 +82,8 @@ class TestMCPToolsComponent(ComponentTestBaseWithoutClient):
             "sse_url": {"show": True, "value": "http://localhost:7860/api/v1/mcp/sse"},
             "tool": {"options": [], "show": True},
             "mode": {"value": "Stdio"},
+            "env": {"show": True, "value": []},
+            "headers_input": {"show": False, "value": []},
         }
 
         # Test switching to Stdio mode