Prepare tkinter for tcl 8.7/9.0 and tk 8.7

[terryjreedy]

@chrstphrchvz Chrisotpher Chavev, who did similar work preparing Perl for these anticipated releases, has opened several issues and PRs to do the the same for tkinter. Likely more will follow until 8.7.0 is released.

This issue is only for tracking these. All PRs should be attached to other issues.

Most of the changes are to tests. We can backport these to 3.11. Even if it is not completely ready for 8.7 when our bug-fixing ends, it will give Linux distributors a head start should they end up distributing both 3.11 and tcl/tk 8.7 simultaneously. We can deal with non-test code changes as they are needed. Anything not backported should be noted below.

• Tkinter: C API changes are needed for Tcl 8.7 and 9.0 value types #103194
  Includes some general comments about the situation and _tkinter.FromObj PR.
• Tk 8.7: TIP 577 breaks tkinter.Menu.index() #103685
• TIP 538 prevents building Tkinter against Tcl 8.7 built with bundled libtommath #103839
  gh-103839: Allow building Tkinter against Tcl 8.7 without external libtommath #103842 not backported to 3.11.
• Tkinter fails to build with Tcl 9.0 due to Tcl_AppInit() undeclared #104363
• Tkinter uses deprecated functions mp_to_unsigned_bin_n() and mp_unsigned_bin_size() #104399
• Tkinter: test_getint incompatible with Tcl 9.0 #104411
• Tkinter: Tk 8.7 quotes pathnames in certain error messages #104494
• Tkinter, IDLE: Future Tcl and Tk can have differing version/patchlevel #104496
• Tkinter: Tk 8.7 alphabetizes options in certain error messages #104497
• IDLE: completions toplevel blank on Tk Aqua 8.7 #104499
• Certain Tkinter tests fail on Tk 8.7 due to TIP 577 #104855
• Tkinter spinbox test failures on Tk 8.7 #104856
• Tkinter: incompatible pointer types warnings when built with Tcl 9 #112672
• IDLE uses incorrect screen dimension units #120104
• Fix tkinter.ttk with Tcl/Tk 9.0 #120211
• Add tests for new Tk widget options #120873

[terryjreedy]

@chrstphrchvz Did you get the email from Zach Ware about triaging?

[chrstphrchvz]

See also gh-112672