[LU-2401] Add ability for lu_key to be allocated upon first get but not during initialization.

• Type: Improvement
• Resolution: Low Priority
• Priority: Major
• Story Points: 1
• Project: Orion
• Assignee: Mikhail Pershin
• Reporter: Mikhail Pershin

Description

This idea arose during llog_thread_info implementation. Often such thread info may not be ever used. The generic mechanism is needed to don't allocate keys if they are might be not needed, but do that upon first get that key.