* refactor: Refactor `PublicParams` initialization (`new`) to use `setup` method

- Updated the function interface for generating `PublicParams` across several files, replacing the `new` method with `setup`.
- The method name change impacts the `benches/recursive-snark-supernova.rs`, `src/supernova/test.rs`, and `src/supernova/mod.rs` files.

* Refactor traits that allows implementing different engines for the same curve cycle (microsoft#263)

* rename Group to Engine

* port tests

* checkpoint

* checkpoint

* compiles

* update benchmarks and tests to use Engine

* rename GroupExt to DlogGroup

* move get_curve_params to Group and rename

* fix doc test; cargo fmt

* inline single trait requirements; fix comments

* cut comment

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Co-authored-by: Srinath Setty <srinath@microsoft.com>