gh-86726: Document tkinter method-name conflicts (GH-151917)

Document where widget methods shadow inherited Misc, geometry-manager and
Wm methods, correct the inaccurate "size/bbox is an alias of
grid_size/grid_bbox" claims, and add "# overrides X" comments at the
definitions.

Also document the geometry-manager ambiguity: the short names forget, info,
slaves, content and propagate are defined by Pack, Place and Grid but
resolve to the pack variant.

Cross-reference the window-manager methods grid, forget and state with the
same-named grid geometry manager, Pack.forget and ttk.Widget.state.

(cherry picked from commit 4de5683)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 2 people