text: Title: refactor: consistent logging
  Body: We support basic logging for doc indices. It's defined in the abstract class and consists of simple logs for `init`, `index`, `find`, `filter` (`filter_batched`) and `text_search` (`text_search_batched`), etc.
  
  The inconsistency is introduced when a specific doc index overrides method(s) listed above, and thus, doesn't use logs defined in the abstract class. As a result, some doc indices will have logs, and others won't. 
  
  **Definition of Done:**
  - [ ] Add logs to document index implementations where needed (i.e. inside the functions that override ones in the abstract class)