Add cargo features to disable by default the frontends when not needed #138
Description
Add cargo features to disable by default the frontends, and then we can turn on the only specific frontend that we want to use (ie. Noir, Circom or Noname for the moment).
The reasoning behind this is that compilation time now is too long, in part because dependencies on specific frontends, so if the compilation don't use some frontend it can be turned off by default.