Make possible to run tests with address sanitizer to quickly check for
memory errors, although we have to disable the error exit code in case of
leaks because we have some which are due to something else down in the stack
(and LSAN suppression files doesn't allow to define the stack to ignore
as we can in valgrind).
However, we'd abort in case of memory errors anyways, so this still helps
to prevent major problems, while still logging the leaks.
In order to run pam module tests with ASAN we need to manually pass the
library to LD_PRELOAD, as we do for the wrapper.
We run a certain number of tests right now, without being able to easily
run them separated or to check which one failed.
So add a script to inspect all the available unittests per each python
script and use it to figure out the tests we can run in meson.
As per this, define a global 'python_tests' variable in meson that allows
to register new python tests easily without having to repeat the settings
for all the tests.
For each test we have, we check if we can fetch a list of unit tests, and
if possible we create a meson test for each one.
Otherwise we just fallback to normal behavior.
This is something that can be hopefully implemented into upstream meson [1].
[1] https://github.com/mesonbuild/meson/issues/6851
