[Feature] Marlin verification gadget with hiding

[weikengchen]

🚀 Feature

This is a pending item to testnet2.

In testnet2, the NoopProgram uses Marlin. The Marlin proof it is using intentionally turns off the "hiding" feature.

The reason why in IVLS the "hiding" feature is turned off is: in IVLS, zero-knowledge is not needed.

In our application, however, this is needed. This would require some changes to the current code:

• let Marlin specify the hiding bounds
• enhance PolyCommit with support of hiding

[weikengchen]

This is done in a few commits to #269, which would be merged into #267 and then into #257.