Problem: ./mlm_selftest can't find .cfg files in mlm_client selftests and fails

[BHare1985]

Solution: Add configure_file calls to CMakeLists

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WARNING: This modifies a zproject generated file.

This is meant as a quick-fix for those stump as to why mlm_client selftest fails with the following when executing mlm_selftest

 * mlm_client:
W: 24-03-27 13:53:44 cannot load config file 'src/mlm_client.cfg'
I: 24-03-27 13:53:44 My address is 'client_robust'
mlm_selftest: /home/brian/malamute/src/mlm_client.c:897: mlm_client_test: Assertion `rc == 0' failed.

When running cmake from clion IDE, the default behavior is that mlm_selftest is it's own test project you can execute, but when doing so the authorization fails (relating to not finding .cfg). I have yet to dive into the depths of how this could be done with zproject properly, and I tried implementing the suggestion of moving them to /src/selftests_ro ( #272 ) but that was honestly a lot of changes and they wouldn't of been valid anyways since they were modifying zproject generated files.

Not reading in mlm_client.cfg failed gracefully with a warning, but sending PLAINto the auth actor with non-existant passwords.cfg is out the scope of malamute (different repo) but would be nice if it also warned.

[BHare1985]

Clarification: zauth does warn about not loading the cfg file but only when VERBOSE is true, which is different than malamute.