Make `--biocontainers` the default test strategy (for managed tests)

It's 2022 and this is the number one reason why tests pass/fail locally and you have a different result on CI.
You can always use `--no_biocontainers` if necessary.

No file or test path is named. Start by locating the managed-test CLI handling for `--biocontainers` and `--no_biocontainers`, then inspect existing tests for their default behavior; done means managed tests use Biocontainers by default while the opt-out remains available.

Written by the indexing model from the issue text.