fix(fetch): reject Request body for GET and HEAD methods

[HiteshShonak]

This Pull Request fixes/closes #5200.

It changes the following:

• into_request_builder now checks if the method is GET or HEAD and throws a TypeError if a body is provided, matching the Fetch Standard.
• Added regression tests for both GET and HEAD cases.

Testing:

cargo test -p boa_runtime request -- --nocapture

Spec reference: https://fetch.spec.whatwg.org/#dom-request

[Copilot]

Pull request overview

This PR aligns Boa’s Request constructor with the Fetch Standard by rejecting request bodies for GET and HEAD methods, addressing issue #5200.

Changes:

• Add a GET/HEAD + body validation in RequestInit::into_request_builder, returning a TypeError when violated.
• Add regression tests asserting new Request(..., { method: "GET"/"HEAD", body: "x" }) throws a TypeError.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
core/runtime/src/fetch/request.rs	Adds GET/HEAD body rejection logic during request construction.
core/runtime/src/fetch/tests/request.rs	Adds regression tests for GET/HEAD requests with an explicit body.

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[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,539	50,539	0
Ignored	1,426	1,426	0
Failed	998	998	0
Panics	2	2	0
Conformance	95.42%	95.42%	0.00%

Tested main commit: 58a24587890677d94618259dfaa5f257ab5ef9c9
Tested PR commit: a31e50ee9f74fc5a7a9a70e849e5eab6359c8fd5
Compare commits: 58a2458...a31e50e

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.81%. Comparing base (6ddc2b4) to head (a31e50e).
⚠️ Report is 913 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5201       +/-   ##
===========================================
+ Coverage   47.24%   59.81%   +12.57%     
===========================================
  Files         476      582      +106     
  Lines       46892    63470    +16578     
===========================================
+ Hits        22154    37965    +15811     
- Misses      24738    25505      +767     

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