feat(stdlib): add Path.removeExtension

[spotandjake]

This adds Path.removeExtension to the Path library as I noticed there wasn't really a great way todo it before

[alex-snezhko]

Would it be better to have an updateExtension/withExtension function that you could just pass in None to remove

[spotandjake]

Would it be better to have an updateExtension/withExtension function that you could just pass in None to remove

I was debating an updateExtension but I honestly think we should still have removeExtension it's more intuitive and clear what it does and then updateExtension can just take a string.

[ospencer]

I think this is reasonable to have. I could additionally see an updateExtension to change it, but I like them being separate because it's easy to search for.