Merge pull request #4176 from esl/parallelise-tests

Rearranged service_domainn_db_SUITE to run more tests in parallel

This PR refactors service_domainn_db_SUITE. New grouping of test cases is introduced. Some of the tests are using randomised domain names so they don't interfere each other.

For MSSQL the test are being run sequentially because of the random fails (due to poor dev container with MSSQL that we use on the CI). To finally check if we don't introduce new flaky tests I ran CI multiple times and none of the time this suite failed - https://app.circleci.com/pipelines/github/esl/MongooseIM/11803.
There are flaky tests in other suites though. I'd be nice if we addressed it in the future.