Exposes a `POST /internal/observability_ai_assistant/chat/recall`
endpoint for [Investigate UI
](#183293). It is mostly just
moving stuff around, some small refactorings and a new way to generate
short ids. Previously we were using indexes for scoring suggestions, we
are now generating a short but unique id (ie 4-5 chars) which generates
a fairly unique token which strengthens the relationship between the id
and the object but still allows for quick output. LLMs are slow to
generate UUIDs, but indexes are very generic and the LLM might not pay a
lot of attention to it.