GeezerVison

The HZ encoder can consume a tilde after writing only its first escape byte. A split ISO-2022 escape can exceed the incremental decoder’s pending buffer, and a reset can leave the previous character set selected. Reserve space for both HZ bytes before consuming the tilde, allow the full pending escape, and restore the initial ISO-2022 state on reset. Keep the native codec table and the active encoder error policy alive so replacing their Python owners cannot leave a codec using freed memory.
(cherry picked from commit a96fbdc)

Manual backport notes (3.15): the automated backport conflicted in multibytecodec_encode() because 3.15 predates the PyBytesWriter conversion (gh-155742). The ERROR_DECREF(errors) calls are added to the existing buf.outobj return and error paths instead; nothing else differs. test_multibytecodec and the CJK codec tests pass with -R 3:3. This is needed before the gh-160185 backport (GH-161067), whose new tests rely on the ISO-2022 reset fix here.

• Issue: Fix minor safety issues #159739