Adds a custom pytest option for archiving logs and conf files

[ichristod]

The purpose of this PR is to enrich python test suite with the capability of log archiving.

With the current situation, httpd/test/gen/apache folder keeps logs and configurations of the last pytest execution either it was about a module or single test.
In addition, if you wanted to compare test results between two httpd versions, you would have to manually preserve the contents of the test/gen/apache/, before cleaning, building and installing a new httpd version.

With the --archive/archive-all option you only need to provide the parameter of the /path/to/archive and it handles the creation and the updates of the archiving folder structure.

I think it helps when you want to compare results across httpd versions.

[ichristod]

@icing I would appreciate a feedback on this one.

[icing]

Since pytest can be invoked for specific tests and test names are designed for this, I do not see the need to add that into the test env itself. My opinion.

One can as well run pytest -k test_h2 and archive the test/gen directory contents where one likes.

I would therefore probably never use that option. But if people think it's useful for them, I'd not stop them.

[ichristod]

I found it useful in my case mainly because if you choose to execute an entire module, test/gen keeps the configuration from the last test execution. So if you want to keep the configuration from each test, that isn’t possible.
A similar issue occurs with logs too, when you execute more than one module you end up with the logs from the last module only.