add URLSearchParams support

[Monti-27]

Fixes #4743.

Adds URLSearchParams and wires up URL.searchParams.

This also fixes the constructor path for iterable inputs, handles explicit undefined correctly in the two-argument has() and delete() overloads, adds runtime coverage, and re-enables the skipped URL WPT case.

Tests:

• cargo test -p boa_runtime --lib
• cargo test --manifest-path tests/wpt/Cargo.toml url -- --nocapture
• cargo clippy -p boa_runtime --all-features --all-targets -- -D warnings

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,073	49,935	-138
Ignored	2,072	2,207	+135
Failed	818	821	+3
Panics	0	0	0
Conformance	94.54%	94.28%	-0.26%

Broken tests (3):

test/intl402/DateTimeFormat/prototype/toStringTag/toStringTag.js (previously Passed)
test/intl402/DateTimeFormat/prototype/toStringTag/toString.js (previously Passed)
test/intl402/Number/prototype/toLocaleString/throws-same-exceptions-as-NumberFormat.js (previously Passed)

Tested main commit: 0698e7063866a1b40be043a1089be43d3224db4b
Tested PR commit: a594311f4748c1f5461953ea54b30877a73f8538
Compare commits: 0698e70...a594311

[Monti-27]

@jedel1043 can you please review this
thank you !!

[Monti-27]

@jedel1043 updated this. searchParams is now created during URL construction and the getter just returns the same object.

[Monti-27]

give me 5 mins I'll clutch this :))

[Monti-27]

also fixed the clippy failure from the missing errors docs on the Rust side URL constructors

[codecov]

Codecov Report

❌ Patch coverage is 89.68481% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.77%. Comparing base (6ddc2b4) to head (de17de0).
⚠️ Report is 896 commits behind head on main.

Files with missing lines	Patch %	Lines
core/runtime/src/url.rs	89.68%	36 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5040       +/-   ##
===========================================
+ Coverage   47.24%   59.77%   +12.53%     
===========================================
  Files         476      580      +104     
  Lines       46892    63559    +16667     
===========================================
+ Hits        22154    37995    +15841     
- Misses      24738    25564      +826     

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[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,079	50,079	0
Ignored	2,072	2,072	0
Failed	812	812	0
Panics	0	0	0
Conformance	94.55%	94.55%	0.00%

Tested main commit: e2ab577394a400f63cd509e7623676241c543876
Tested PR commit: de17de0091100b6773e766636567fc35292ec186
Compare commits: e2ab577...de17de0