Implement i128/u128 to JsBigInt conversions

[AlvinKuruvilla]

This commit implements trait conversions to JsValue for i128/u128. This addresses #1970

This Pull Request fixes/closes #{1970}.

It changes the following:

• Adds trait conversions for the missing i128 and u128 rust types to JsValue

[Razican]

Hmmm I'm not sure if we want to do this. There is no native type in JavaScript equivalent to i/u128. And using a BigInt is not the same thing, since it's stored in the heap and performance is different.

I could see a TryFrom implementation that tries to convert it to an i32, though. Or to an f64 if there is no precision loss.

But in general, I wouldn't do this conversion, different users might have different thoughts on how should this work.

[AlvinKuruvilla]

@Razican thanks for getting back to me.
Yeah, that makes sense, I saw this issue open and without activity, so I thought it might be a good way to get my feet wet. Is there no longer any interest in doing this, though?

[jedel1043]

Hmmm I'm not sure if we want to do this. There is no native type in JavaScript equivalent to i/u128. And using a BigInt is not the same thing, since it's stored in the heap and performance is different.

Note that this PR implements From for JsBigInt and Numeric, not JsValue, and both traits are also implemented for i/u64.

[jedel1043]

I'd support merging this change. Converting to Numeric is a lot more explicit about allocations than directly converting to JsValue, and if we want to make it a lot more explicit we could specify on the Numeric docs that all conversions from integer types allocate.

[codecov]

Codecov Report

Merging #3129 (57de737) into main (0cc4322) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #3129      +/-   ##
==========================================
- Coverage   50.65%   50.61%   -0.04%     
==========================================
  Files         444      444              
  Lines       42661    42696      +35     
==========================================
+ Hits        21608    21612       +4     
- Misses      21053    21084      +31     

Impacted Files	Coverage Δ
boa_engine/src/bigint.rs	68.14% <0.00%> (-2.09%)	⬇️

... and 5 files with indirect coverage changes

[HalidOdat]

Looks good! just some small nitpicks :)