fix: Use PyObject_VisitManagedDict() of Python 3.13 (#4973)

* fix: Use PyObject_VisitManagedDict() of Python 3.13

Use PyObject_VisitManagedDict() and PyObject_ClearManagedDict() in
pybind11_traverse() and pybind11_clear() on Python 3.13 and newer.

* Add Python 3.13 CI

* tests: don't get numpy/scipy on 3.13 yet

* ci: move 3.13 to upstream

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

.github/workflows/ci.yml

@@ -75,7 +75,6 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python }}
-        allow-prereleases: true
 
     - name: Setup Boost (Linux)
       # Can't use boost + define _

.github/workflows/upstream.yml

@@ -13,13 +13,12 @@ concurrency:
 
 env:
   PIP_BREAK_SYSTEM_PACKAGES: 1
-  PIP_ONLY_BINARY: ":all:"
   # For cmake:
   VERBOSE: 1
 
 jobs:
   standard:
-    name: "🐍 3.12 latest • ubuntu-latest • x64"
+    name: "🐍 3.13 latest • ubuntu-latest • x64"
     runs-on: ubuntu-latest
     # Only runs when the  'python dev' label is selected
     if: "contains(github.event.pull_request.labels.*.name, 'python dev')"
@@ -27,10 +26,11 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - name: Setup Python 3.12
+    - name: Setup Python 3.13
       uses: actions/setup-python@v5
       with:
-        python-version: "3.12-dev"
+        python-version: "3.13"
+        allow-prereleases: true
 
     - name: Setup Boost
       run: sudo apt-get install libboost-dev