[3.12] gh-126997: Fix support of non-ASCII strings in pickletools (GH-127062) (GH-127095)

* Fix support of STRING and GLOBAL opcodes with non-ASCII arguments.
* dis() now outputs non-ASCII bytes in STRING, BINSTRING and
  SHORT_BINSTRING arguments as escaped (\xXX).
(cherry picked from commit eaf217108226633c03cc5c4c90f0b6e4587c8803)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>