gh-153741: Harden IDLE GUI tests for newer Tk and display scaling (#153742)

gh-153741: Harden IDLE GUI tests for newer Tk and display scaling (#153742)

In test_sidebar.test_mousewheel, only use the X11 <Button-4>/<Button-5> events when testing on
x11 Tk before 8.7.  Otherwise, use <Mousewheel> as on other systems.

In test_configdialog, assert the 'disabled' state flag alone instead of
the exact ttk state tuple (which transient pointer states break), and
restore the tests' method masks with addCleanup().

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>