- Improve function names
- Order state updates to be more readable, logical

Use `requestAnimationFrame' to ensure scrollToBottom called after page
content is rendered.

Previously the page wouldn't always scroll to the bottom of the page
on conversation first load

Khoj paginates fetching older messages in conversation on scroll
up.

Previously the older chat message fetch and render on scroll would
lose the earlier scroll position and message in focus. This was very
disorienting.

Use refs to anchor scroll on oldest previously fetched message. This
improves reliability on scroll across different screen widths

Render empty chat messages div to get stable message index to scroll
to. Set the display to none to keep view same as before, as chat
message box shouldn't be visible while Khoj is thinking

This should ease scrolling up to disable auto scroll when Khoj
response being streamed