Enable PYTHONTRACEMALLOC on Windows CI and add CI/CD docs

- Add PYTHONTRACEMALLOC=1 on Windows runners to debug gc errors with popen objects in test_case_cwd_evil[git]

Author: RonnyPfannschmidt

.github/workflows/python-tests.yml

@@ -44,6 +44,9 @@ jobs:
         include:
         - os: windows-latest
           python_version: 'msys2'
+    env:
+      # Enable tracemalloc to debug gc errors with popen objects (especially on Windows)
+      PYTHONTRACEMALLOC: "1"
 
     name: ${{ matrix.os }} - Python ${{ matrix.python_version }}
     steps: