Add Python 3.15 tkinter updates

[JelleZijlstra]

Adds the remaining tkinter portion of the Python 3.15 stdlib updates and removes the matching 3.15 stubtest allowlist entries that are now covered by the stub.

Changes:

• Added tkinter.Event.detail and tkinter.Event.user_data for Python 3.15 (CPython source: https://github.com/python/cpython/blob/bc1be4f6174086b4a46e3fe656552f5bb4e6e7b2/Lib/tkinter/__init__.py#L258-L260)
• Added pack_content, grid_content, and place_content geometry methods for Python 3.15 (CPython source: https://github.com/python/cpython/blob/bc1be4f6174086b4a46e3fe656552f5bb4e6e7b2/Lib/tkinter/__init__.py#L1901-L2056)
• Added the Python 3.15 Text.search options and Text.search_all (CPython source: https://github.com/python/cpython/blob/bc1be4f6174086b4a46e3fe656552f5bb4e6e7b2/Lib/tkinter/__init__.py#L4115-L4169)

[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]