Added a bunch more tests

[Razican]

As a follow up of #2883 and #2884, this PR changes the following:

• Changed the boa_parser::error::ErrorContext trait, to now have a set_context() and context() setter and getters for context.
• Added unit tests for parser and lexer errors.
• Added 100% testing coverage to boa_unicode
• Added tests for Source
• Unified output for parser and lexer errors

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	94,601	94,601	0
Passed	73,293	73,293	0
Ignored	17,540	17,540	0
Failed	3,768	3,768	0
Panics	0	0	0
Conformance	77.48%	77.48%	0.00%

[codecov]

Codecov Report

Merging #2885 (0942295) into main (c738b50) will increase coverage by 0.20%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2885      +/-   ##
==========================================
+ Coverage   51.24%   51.44%   +0.20%     
==========================================
  Files         427      427              
  Lines       42522    42621      +99     
==========================================
+ Hits        21790    21928     +138     
+ Misses      20732    20693      -39     

Impacted Files	Coverage Δ
boa_engine/src/builtins/uri/mod.rs	21.83% <ø> (ø)
boa_engine/src/value/conversions/serde_json.rs	75.75% <ø> (ø)
...src/parser/expression/assignment/arrow_function.rs	76.82% <ø> (ø)
...rser/expression/assignment/async_arrow_function.rs	0.00% <ø> (ø)
boa_parser/src/source.rs	100.00% <ø> (+62.50%)	⬆️
boa_unicode/src/lib.rs	66.66% <ø> (+66.66%)	⬆️
boa_parser/src/error/mod.rs	100.00% <100.00%> (ø)
boa_parser/src/lexer/error.rs	100.00% <100.00%> (+41.66%)	⬆️

... and 28 files with indirect coverage changes

[Razican]

I've missed a few lines, so I will adapt the tests a bit :)

[Razican]

Misses in coverage have been reported here: xd009642/tarpaulin#351 (comment)

[Razican]

@HalidOdat I removed ut_ prefixes in our codebase. I also removed them from places where we were already using them before. Let me know your thoughts :)

[HalidOdat]

This looks perfect to me! :)

[jedel1043]

Looks great!