Using unstable sort for sorting keys on to_json() for GC objects

[Razican]

This solves the clippy warning we were getting, and it might speed up things a bit. As far as I understand, there is no need to use stable sorting, right? Especially since we don't have two keys with the same name.

[codecov]

Codecov Report

Merging #833 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #833   +/-   ##
=======================================
  Coverage   59.26%   59.26%           
=======================================
  Files         157      157           
  Lines       10035    10035           
=======================================
  Hits         5947     5947           
  Misses       4088     4088           

Impacted Files	Coverage Δ
boa/src/object/gcobject.rs	73.23% <100.00%> (ø)

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[github-actions]

Benchmark for 17ac8bd

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Test	PR Benchmark	Master Benchmark	%
Arithmetic operations (Execution)	364.3±0.90ns	359.7±3.91ns	+1.28%
Arithmetic operations (Full)	234.1±1.28µs	225.1±2.99µs	+4.00%
Array access (Execution)	7.8±0.06µs	7.8±0.09µs	0.00%
Array access (Full)	250.9±1.50µs	246.9±2.82µs	+1.62%
Array creation (Execution)	2.8±0.01ms	2.8±0.03ms	0.00%
Array creation (Full)	3.0±0.01ms	3.0±0.02ms	0.00%
Array pop (Execution)	1049.3±6.56µs	1039.1±11.06µs	+0.98%
Array pop (Full)	1462.9±9.46µs	1443.3±15.77µs	+1.36%
Boolean Object Access (Execution)	4.6±0.01µs	4.6±0.05µs	0.00%
Boolean Object Access (Full)	242.6±4.17µs	236.9±2.95µs	+2.41%
Clean js (Execution)	701.5±4.37µs	695.5±7.63µs	+0.86%
Clean js (Full)	979.0±6.05µs	967.4±10.97µs	+1.20%
Clean js (Parser)	36.8±0.26µs	36.2±0.62µs	+1.66%
Create Realm	461.0±3.03ns	464.6±8.31ns	-0.77%
Dynamic Object Property Access (Execution)	5.5±0.04µs	5.5±0.07µs	0.00%
Dynamic Object Property Access (Full)	247.9±1.27µs	240.3±3.57µs	+3.16%
Expression (Parser)	6.9±0.04µs	6.9±0.09µs	0.00%
Fibonacci (Execution)	807.3±3.48µs	805.5±8.63µs	+0.22%
Fibonacci (Full)	1075.6±8.70µs	1062.9±11.15µs	+1.19%
For loop (Execution)	22.1±0.14µs	21.7±0.26µs	+1.84%
For loop (Full)	268.9±0.83µs	267.7±2.79µs	+0.45%
For loop (Parser)	18.0±0.09µs	17.6±0.21µs	+2.27%
Goal Symbols (Parser)	12.4±0.08µs	12.3±0.15µs	+0.81%
Hello World (Parser)	3.1±0.01µs	3.0±0.04µs	+3.33%
Long file (Parser)	754.1±5.13ns	752.1±9.94ns	+0.27%
Mini js (Execution)	628.4±5.42µs	624.6±8.05µs	+0.61%
Mini js (Full)	881.9±9.37µs	862.7±11.02µs	+2.23%
Mini js (Parser)	32.3±0.19µs	31.4±0.45µs	+2.87%
Number Object Access (Execution)	3.6±0.01µs	3.6±0.06µs	0.00%
Number Object Access (Full)	240.3±0.97µs	236.4±3.30µs	+1.65%
Object Creation (Execution)	4.7±0.05µs	4.7±0.05µs	0.00%
Object Creation (Full)	240.4±1.49µs	242.2±2.09µs	-0.74%
RegExp (Execution)	9.5±0.05µs	9.4±0.12µs	+1.06%
RegExp (Full)	247.2±1.32µs	242.3±3.09µs	+2.02%
RegExp Literal (Execution)	10.5±0.07µs	10.6±0.11µs	-0.94%
RegExp Literal (Full)	253.5±1.98µs	243.4±2.90µs	+4.15%
RegExp Literal Creation (Execution)	9.4±0.07µs	9.5±0.10µs	-1.05%
RegExp Literal Creation (Full)	245.1±1.49µs	241.6±3.95µs	+1.45%
Static Object Property Access (Execution)	4.9±0.02µs	5.0±0.05µs	-2.00%
Static Object Property Access (Full)	242.3±1.23µs	240.1±2.67µs	+0.92%
String Object Access (Execution)	6.9±0.27µs	6.8±0.07µs	+1.47%
String Object Access (Full)	243.8±2.70µs	243.0±2.22µs	+0.33%
String comparison (Execution)	6.4±0.04µs	6.3±0.06µs	+1.59%
String comparison (Full)	258.9±16.01µs	240.9±3.00µs	+7.47%
String concatenation (Execution)	5.2±0.03µs	5.2±0.08µs	0.00%
String concatenation (Full)	244.7±3.33µs	235.8±2.76µs	+3.77%
String copy (Execution)	4.0±0.02µs	4.0±0.05µs	0.00%
String copy (Full)	235.0±1.26µs	231.8±3.16µs	+1.38%
Symbols (Execution)	3.4±0.02µs	3.4±0.04µs	0.00%
Symbols (Full)	225.8±5.16µs	221.5±2.25µs	+1.94%