Circuits/gadgets refactoring

[XuyangSong]

We've Implemented a bunch of independent circuits used inside of Taiga.(e.g. conditional_equal, conditional_select, hash_to_curve, note_encryption, blake2 hash, etc, etc.). It would be better to refactor the circuits to an independent sub-library inside of Taiga so that external projects can use it.

• refactor the underlying circuits/garages/chips to be more friendly to use, add necessary use cases and annotation.
• create an independent circuit sub-library in Taiga.