lsifstore: refactor API docs text search utilities into separate package
Created by: slimsag
Keeping lsifstore
logic more isolated, as I add querying logic there's a bit of complexity for composing queries against the DB (including this code for lexeme management, etc.) that is nice to keep isolated in a separate package.
Helps #21938
Signed-off-by: Stephen Gutekanst [email protected]