Implement String.prototype.split

[jevancc]

This Pull Request implements String.prototype.split

It changes the following:

• Add the method implementation
• Add unit tests

[codecov]

Codecov Report

Merging #1026 (1a89274) into master (553ea52) will increase coverage by 0.07%.
The diff coverage is 81.08%.

@@            Coverage Diff             @@
##           master    #1026      +/-   ##
==========================================
+ Coverage   58.69%   58.77%   +0.07%     
==========================================
  Files         172      172              
  Lines       11745    11782      +37     
==========================================
+ Hits         6894     6925      +31     
- Misses       4851     4857       +6     

Impacted Files	Coverage Δ
boa/src/builtins/string/mod.rs	62.80% <81.08%> (+1.46%)	⬆️
boa/src/object/gcobject.rs	67.93% <0.00%> (+0.34%)	⬆️

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[Razican]

I will check the code through the day, but the conformance increase looks really good :)

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,493	78,493	0
Passed	23,989	24,125	+136
Ignored	15,585	15,585	0
Failed	38,919	38,783	-136
Panics	100	100	0
Conformance	30.56	30.74	+0.17%

[jevancc]

@Razican The three extra panics come from built-ins/map/prototype/keys/returns-iterator.js (no Set implementation) and test/built-ins/string/prototype/split/cstm-split-get-err.js (bug in Object.defineProperty). I have no idea why they did not panic in the master branch but here.

[Razican]

I have no idea why they did not panic in the master branch but here.

I would guess this now enables some tests to run further, which shows some panics that did not appear before because it was failing early.

[Razican]

It's looking good! I added some sugestions to make the code a bit more idiomatic :)

[RageKnify]

Looks good, noted a few improvements to be closer to the spec.

[Razican]

Looks good, let's merge it :)