(SP: 2) Enhance chat search

[ipasic-softserve]

The current chat search functionality only works with the messages that are currently loaded, not across all messages:

This needs to be updated so that the search covers all messages, both loaded and unloaded.

Example: If a user searches for the term "test" and there is one match in the 10 currently loaded messages, but another match exists 40 messages back, the system should load all 40 messages and display the relevant matches.