INTEG-249: [Unified Search] Externalize the fuzzy search setting

Fix description:
* Remove the hard-coded fuzzy search operator
* Allow administrators to activate/deactivate this option and tune similarity value
* Validate the similarity value.
* Handle the tilde character in user query in both cases of fuzzy setting.
Merge commit '752352afd01219e32354a8b5039da5df9a46af48' into HEAD