change models to use friendlier names for init

[mochic]

Uses populate_by_name, serialization_alias, and validation_alias to create more friendly names for SlimsBaseModel when initializing a new model from model constructor.

[patricklatimer]

As discussed, this makes the code look a little uglier, requiring both validation_alias and serialization_alias, but there's currently not a great way around that with Pydantic and it definitely makes the interface significantly better.