[wasm][coreclr] Implement RhpNewArrayFastAlign8

[radekdoulik]

Resolves#120659

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[Copilot]

Pull Request Overview

This PR implements the RhpNewArrayFastAlign8 function for WASM and CoreCLR, resolving issue #120659. The implementation enables aligned memory allocation for arrays that require 8-byte alignment, particularly for long and double arrays on 32-bit platforms.

Key changes:

• Implements the RhpNewArrayFastAlign8 function with proper alignment logic
• Refactors existing allocation code to improve maintainability
• Removes WASM-specific test exclusions that are no longer needed

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/runtime/portable/AllocFast.cpp	Implements RhpNewArrayFastAlign8 function and refactors allocation helpers
src/tests/JIT/interpreter/Interpreter.cs	Removes WASM architecture exclusions for long and double array tests

[AaronRobinsonMSFT]

Overall, LGTM. I'm like to try and remove some of the "magic" numbers in NewArrayFastAlign8Core. There must be some simple macros or computation to get them.