Feat: Improve visibility of Unleash lifetime configuration

[daveleek]

Is your feature request related to a problem? Please describe.
We get occasional reports of cache file locks that we often suspect are caused by having too many instances of Unleash running concurrently in one process/app.
We should improve the visibility of how Unleash lifetime is configured runtime for debugging purposes (make it easier for developers to figure out if this is the cause) and improve clarity of Unleash lifetime configuration recommendations in Docs

Describe the solution you'd like

• Explicit logging of the quantity of Unleash instances running in the process/app
• Log warnings when the counter reaches a threshhold
• Improve docs to reflect recommended practises around Unleash lifetime configuration