Added random_state as an available hyper parameter for xgboost models

[SilasMarvin]

I followed the standard found throughout the repo and just called unwrap on line 166. This does have the potential to cause somewhat confusing error messages if they have malformed arguments. I would be happy to go through and replace the unwrap() calls with expect(SOME HELPFUL ERROR MESSAGE) throughout pgml-extension if that would be helpful?

[montanalow]

You're right. expect() is preferable to unwrap(), but rather than trying to convert all existing cases, I think it'd be better to try to move most functions that currently unwrap to instead return an anyhow::Result, and add context() to their calls for better nested function call clarity.

I think the current transformer bindings for transform and embed are the worst offenders with the mostly likely failure cases, and the scikit algorithm's are probably second worst on that front.