Add tkinter Entry and Spinbox validate methods

[serhiy-storchaka]

The Tk validate widget command of the entry and spinbox widgets has no tkinter wrapper and is currently reachable only through tk.call().

pathName validate forces an evaluation of the -validatecommand, independently of the conditions specified by the -validate option (by temporarily setting -validate to all), and returns whether the value is valid.

I propose to add the corresponding Entry.validate() and Spinbox.validate() methods.

Linked PRs

• gh-151878: Add tkinter Entry and Spinbox validate methods #151879