Issue 49381 - Refactor numerous suite docstrings
Description: We need to have properly formatted and detailed docstrings
in all existing test suites.
Suites that were changed in this commit: config, autotuning,
range_search, paged_results, psearch, sasl plain.
Also, fix constants in sasl plain suite and remove :feature:
from create_test.py tool, it's not mandatory anymore.
https://pagure.io/389-ds-base/issue/49381
Reviewed by: amsharma, vashirov (Thanks!)