Generic merkle tree lib #124
Description
We use a lot of merkle trees, with duplicate code and implementations. While they are not excatly the same, cause they have different parameters, placeholders, etc and in some cases they are sparse (such as the JMT), we can probably unify them and make a small depts that implement a normal and a sparse merkle tree with configurable parameters. Specifically we use them for:
- Sigsum (normal)
- Sigstore (normal)
- Block header hash (normal)
- List storage (JMT)
It would reduce the code footprint, and also have more consistent (and auditable) implementations,