Add more Python 3.15 stdlib updates

[JelleZijlstra]

Adds another small batch of Python 3.15 stdlib updates, and removes the matching 3.15 stubtest allowlist entries.

Changes:

• Removed ctypes.SetPointerType for Python 3.15; ARRAY remains available (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/ctypes/__init__.py)
• Removed glob.glob0 and glob.glob1 for Python 3.15 (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/glob.py#L135-L142)
• Changed the Python 3.15 default for gzip.compress(compresslevel=...) (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/gzip.py#L622)
• Changed the Python 3.15 default marshal format version for marshal.dump and marshal.dumps (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Include/cpython/marshal.h#L9)
• Added the on_error keyword-only parameter to forkserver preload helpers (CPython sources: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/multiprocessing/context.py#L186 and https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/multiprocessing/forkserver.py#L68)
• Changed pdb.Pdb.print_stack_entry(prompt_prefix=...) to default to None for Python 3.15 (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/pdb.py#L2644)
• Added pkgutil.resolve_name(strict=...) for Python 3.15 (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/pkgutil.py#L407)
• Updated pprint defaults for Python 3.15 (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/pprint.py#L46-L81)
• Added site.process_startup_files and the defer_processing_start_files keyword-only parameter for Python 3.15 (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/site.py#L356-L593)
• Added symtable.symtable(module=...) for Python 3.15 (CPython source: https://github.com/python/cpython/blob/1162834c0ee310f7497b4f9d18d17a998e26831c/Lib/symtable.py#L20)

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

pandas (https://github.com/pandas-dev/pandas)
- pandas/core/computation/ops.py:328: error: Need type annotation for "_binary_ops_dict" (hint: "_binary_ops_dict: dict[<type>, <type>] = ...")  [var-annotated]