catch a panic in merkle proof verification

[themighty1]

Currently, there is a panic in winterfell's crypto crate when verifying a Merkle proof, see facebook/winterfell#200
The lib assumes that the prover honestly informs the verifier about the total amount of leaves in the tree as well as the leaf indices being proved.

The same type of assumption and panics are present in other merkle libs:
antouhou/rs-merkle#20
https://github.com/rozbb/ct-merkle/blob/e29d123e1b45b0e652e5ee5e4c288ff3792652e5/src/batch_inclusion.rs#L404

Until this issue is fixed upstream, we should wrap the verification in panic::catch_unwind.

[antouhou]

Hi! I'm the author of the rs_merkle library used by this project. The issue has been fixed in the rs_merkle 1.4.1. Please update it in your dependencies! Thank you!

[sinui0]

Thank you @antouhou !