fix(fetch): handle BufferSource bodies in Response

[iammdzaidalam]

Closes #5216

Adds BufferSource handling to the Response() constructor body extraction path.

Currently, inputs like Uint8Array or DataView fall through to stringification,
so binary bodies end up as strings (e.g. "[object Uint8Array]") instead of raw bytes.

This change:

• handles ArrayBuffer, typed arrays, and DataView
• slices typed array / DataView inputs using byteOffset / byteLength
• uses usize::try_from(...) for offsets/lengths to avoid truncation on 32-bit targets
• preserves the existing string fallback for non-binary inputs
• leaves other BodyInit types (e.g. Blob, FormData) for follow-up

Testing

Added tests in core/runtime/src/fetch/tests/response.rs covering:

• ArrayBuffer
• Uint8Array
• subarray/view slicing
• DataView with non-zero offset/length
• string fallback behavior
• content-type behavior (binary vs string)

Notes

• binary bodies do not inject a default Content-Type
• string bodies still default to text/plain;charset=UTF-8

[github-actions]

Test262 conformance changes

Test result	main count	PR count	difference
Total	52,963	52,963	0
Passed	50,539	50,545	+6
Ignored	1,426	1,426	0
Failed	998	992	-6
Panics	2	2	0
Conformance	95.42%	95.43%	+0.01%

Fixed tests (6):

test/intl402/DateTimeFormat/test-option-date-time-components.js (previously Failed)
test/intl402/DateTimeFormat/constructor-options-order.js (previously Failed)
test/intl402/DateTimeFormat/constructor-options-throwing-getters.js (previously Failed)
test/intl402/DateTimeFormat/constructor-options-style-conflict.js (previously Failed)
test/intl402/DateTimeFormat/constructor-options-order-timedate-style.js (previously Failed)
test/intl402/DateTimeFormat/constructor-options-invalid-explicit-components.js (previously Failed)

Tested main commit: 58a24587890677d94618259dfaa5f257ab5ef9c9
Tested PR commit: 8190a7b88ad8f877ccf14a77c2b99b28c83cf433
Compare commits: 58a2458...8190a7b

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.83%. Comparing base (6ddc2b4) to head (8190a7b).
⚠️ Report is 929 commits behind head on main.

Files with missing lines	Patch %	Lines
core/runtime/src/fetch/response.rs	92.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #5217       +/-   ##
===========================================
+ Coverage   47.24%   59.83%   +12.59%     
===========================================
  Files         476      582      +106     
  Lines       46892    63485    +16593     
===========================================
+ Hits        22154    37988    +15834     
- Misses      24738    25497      +759     

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[iammdzaidalam]

Hey @jedel1043, any updates here when you get a moment?

[iammdzaidalam]

hey @jedel1043 @nekevss ,any updates when u get a moment?