update MinHash constructor API in Rust to use scaled instead of max_hash

[ctb]

In #1128, we are deprecating the old max_hash parameter in favor of the new scaled parameter. They can be interconverted easily with no additional information (see functions _get_max_hash_for_scaled and _get_scaled_for_max_hash).

However, it is hard to fully remove max_hash from the Python API because it is used in the Rust API as well!
See the call to lib.kmerminhash_new in sourmash/minhash.py:MinHash.__init__ (currently in #1128 only).

So the goal of this issue is to swap out the max_hash parameter with the scaled parameter in the Rust API.

There are two places to do this in Rust - one is in the kmerminhash_new function, and the other is in the KmerMinHash::new code. I would suggest starting with the former and doing the conversion there, so that
we can get the API bridge between Python and Rust working first, but YMMV :)

Some suggestions for getting started -

• get a full Python and Rust development environment up and running per the docs
• dig into the implementation of kmerminhash_newin src/core/src/ffi/minhash.rs
• add the scaled_to_max_hash and max_hash_to_scaled conversion functions into Rust
• swizzle the mx parameter over to scaled in kmerminhash_new and then convert it to max_hash before passing it into the ::new method.

[ctb]

(please indicate if you are planning to work on this but don't yet have a PR up - thanks! we suggest creating a PR early on in the process, but if you don't want to, please "claim" this issue so that others don't work on it in tandem!)

[xmnlab]

@ctb thanks for the detailed information. I am starting to work on that. thanks :)

[luizirber]

Note that we want to keep max_hash internally (in Rust), because it's easier to use in .add_hash. scaled_for_max_hash and max_hash_for_scaled are already implemented