Add a function to perform the DKG round 1

[andiflabs]

The purpose of this function is to add all the Iron Fish specific functionality, like encryption and input checksumming.

For now this performs the same functionality as the function in iron-fish/ironfish#4885.

[andiflabs]

Once the changes in #44 are merged, we can change the return value from (Vec, Vec) to a dedicated struct (I didn't do it to avoid duplicating the work that @hughy is doing)