Lock workflows for web clients only

What does this MR do and why?

Opening the same workflow in different tabs should be locked; otherwise, it causes confusion. But for other use cases, we can omit lock as it doesn't behave properly at the moment.

The functionality is behind a feature flag, so we can disable it once we find the root cause of improper locking behavior.

Related issue: [FF] `lock_workflows_for_web_only` -- Controls ... (#591407)