[3.11] gh-86493: Fix possible leaks in modules initialization: _curses_panel, _decimal, posix, xxsubtype (GH-106767) (GH-106849) (GH-106851)

(cherry picked from commit 745492355b94d109e47827e5865846f25ae42d26)
(cherry picked from commit 970cb8eabaaf5a8311f1aba4ca4968ef7385fce8)