bpo-32962: Fix test_gdb failure in debug build with -mcet -fcf-protection -O0 (GH...

bpo-32962: Fix test_gdb failure in debug build with -mcet -fcf-protection -O0 (GH-9656) (GH-9788)

When Python is built with the intel control-flow protection flags,
-mcet -fcf-protection, gdb is not able to read the stack without
actually jumping inside the function. This means an extra
'next' command is required to make the $pc (program counter)
enter the function and make the stack of the function exposed to gdb.

test_gdb: get_gdb_repr() now uses the "backtrace 1" command after
breakpoint, as in the master branch.

Co-Authored-By: Marcel Plch <gmarcel.plch@gmail.com>
(cherry picked from commit 9b7c74ca32d1bec7128d550a9ab1b2ddc7046287)
(cherry picked from commit 79d21331e605fdc941f947621846b8563485aab6)