Add structured version info for tkinter

Feature or enhancement

The version of the Tcl and Tk libraries used for building _tkinter is only available as _tkinter.TCL_VERSION/TK_VERSION (strings with only major and minor, like '8.6') and tkinter.TclVersion/TkVersion (the same as floats). The full patch level is not exposed, although the module uses it (TCL_PATCH_LEVEL), and there is no structured form. The runtime version is available as Misc.info_patchlevel(), which needs a Tcl interpreter.

Add _tkinter.TCL_PATCH_LEVEL and _tkinter.TK_PATCH_LEVEL for the full build-time version strings, and tkinter.TCL_VERSION_INFO and tkinter.TK_VERSION_INFO, named tuples of the same type as returned by info_patchlevel(), with fields major, minor, micro, releaselevel and serial.

Linked PRs

• gh-157516

检查现有的 _tkinter.TCL_VERSION/TK_VERSION 和 tkinter.TclVersion/TkVersion API，然后比较 tkinter.Misc.info_patchlevel() 的元组形状。完成的标准是公开两个补丁级别常量，以及两个包含 major、minor、micro、releaselevel 和 serial 字段的命名元组；gh-157516 已经关联。