[Obs AI Assistant] Add documentation on conversation sharing

[mdbirnstiehl]

Conversation sharing options aren't documented in the Observability AI Assistant documentation. Shares some options with Security (Private and Shared): https://www.elastic.co/docs/solutions/security/ai/ai-assistant#share-conversations.

The Obs AI Assistant also has conversation duplicating, archiving capabilities.

Applies from 8.19/9.1

[viduni94]

Thanks for creating this @mdbirnstiehl
The Obs AI Assistant also has conversation duplicating, archiving capabilities.

[mdbirnstiehl]

Thanks, @viduni94! I'll add that to the issue.