Create HintDBs with the discriminated option

According to the documentation
https://coq.inria.fr/distrib/current/refman/proof-engine/tactics.html#coq:cmd.create-hintdb,
when creating a hint database without discrimination, Coq uses the
legacy implementation, which only uses Discrimination Trees for goals
without evars and does not use opaqueness information. This commit
switches the hint databases of stdpp to the new implementation.