feat(stdlib): isNaN and isFinite utility functions for Number

[cician]

This pull request adds two functions to the number module:

isFinite: (Number) -> Bool
isNaN: (Number) -> Bool

So we want explicit isInfinity and isNegativeInfinity as well?

Internally they depend on isBoxedNumber from runtime/numbers so if you don't mind I'd export it.

Technically there's duplicate code in numberUtils, but it's only for WasmF64 and just two lines of actual code. So I don't know if we want to bother reusing it.

Tests could benefit from waiting for PR #720 I guess.

[peblair]

Thanks, this looks great! A couple of notes (aside from the suggested comments):

• We indent the code in the standard library with two spaces, so if you could update these functions to match that style, it would be very helpful.
• With respect to other useful functions, I think an isInfinite function (returning true for positive and negative infinity) would round all of this out nicely. This is what other languages (e.g. Python, Racket) appear to do. I'm not strictly opposed to isPositiveInfinity/isNegativeInfinity as well, but I am not sure it's necessary when users can do isInfinite(x) && x > 0. Wondering what @ospencer's thoughts are.
• Finally, when making the above change(s), can you rebase this onto the latest main?

[phated]

I love how readable this is, even to me!

[ospencer]

Looks awesome! I agree with @peblair that isInfinite is a fine choice here 👍

Left you some tiny tweaks to your code comments, but otherwise this is perfect!

[ospencer]

Thanks so much @cician!