Move test framework to Trixie

[squell]

Bookworm is now oldstable. I propose the test framework gets ported to trixie.

This has some implications:

• The test case default_and_override_pam_env_vars_are_parentheses_checked_but_set_vars_are_not fails, due to PAM giving a "critical error", and should be disabled.

  This is also the case for ogsudo -- this is such a freak thing that it could trigger a null pointer dereference. We haven't figured out yet 100% why this crash happens -- there has been a change in the parsing code in PAM which makes it not like the PAM config we have in our test.

• There are two tests on which ogsudo has different behaviour in the Trixie version.