tests: remove legacy functions / tests

[casperklein]

Description

In old bats versions, there was no native support for the setup_file, teardown_file functions. To get this working, workaround functions and dummy tests (@test "first, @test "last") were added.

Since our bats version does support those functions out-of-the-box for some time now and there is no need for the dummy functions / test anymore, they have been removed.

CI: This will also remove plenty of message like this while running the tests:

ok 5 first # skip This version natively supports setup/teardown_file

@martin-schulze-vireso IIRC, you wrote most of these tests. I wasn't able to add you as a reviewer, but you might also take a look and confirm, if everything is alright.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Improvement (non-breaking change that does improve existing functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README.md or the documentation under docs/)
• If necessary I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[martin-schulze-vireso]

LGTM

Its funny how this issue made me end up as maintainer of Bats... Nice to see my work bear fruit. Thanks @ALL for giving docker-mailserver new drive.

[georglauterbach]

Very nince! This was bothering me for a long time now.