Adding support for aligning AllocateTypeAssociatedMemory

[tannergooding]

This resolves #118897

[Copilot]

Pull request overview

This PR adds support for aligned memory allocation in the AllocateTypeAssociatedMemory API by introducing a new overload that accepts an alignment parameter. The implementation covers all three runtime variants (CoreCLR, Mono, and NativeAOT) and includes test coverage for the new functionality.

Key Changes

• Added new AllocateTypeAssociatedMemory(Type, int, int) overload with alignment parameter across all runtime implementations
• Updated XML documentation for existing overload to match new style guidelines
• Implemented validation to ensure alignment is a power of 2
• Added comprehensive test cases for both valid and invalid argument scenarios

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/libraries/System.Runtime/ref/System.Runtime.cs	Added public API signature for the new aligned allocation overload
src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs	CoreCLR managed implementation with QCall to native code
src/coreclr/vm/runtimehandles.h	Added native function declaration for aligned allocation
src/coreclr/vm/runtimehandles.cpp	CoreCLR native implementation using LoaderHeap::AllocAlignedMem
src/coreclr/vm/qcallentrypoints.cpp	Registered new QCall entry point for aligned allocation
src/mono/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.Mono.cs	Mono implementation using NativeMemory.AlignedAlloc
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.NativeAot.cs	NativeAOT implementation using NativeMemory.AlignedAlloc
src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Runtime/CompilerServices/RuntimeHelpersTests.cs	Added test coverage for both invalid and valid arguments

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-runtime-compilerservices
See info in area-owners.md if you want to be subscribed.

[tannergooding]

Removed the note and added tests for a few key sizes from 1-256kb:

[InlineData(1)]
[InlineData(2)]
[InlineData(4)]
[InlineData(8)]      // .NET largest natural alignment
[InlineData(16)]     // V128, typical max_align_t
[InlineData(32)]     // V256
[InlineData(64)]     // V512, typical cache line size
[InlineData(128)]    // less typical cache line size
[InlineData(512)]    // historical disk sector size
[InlineData(4096)]   // typical disk sector and page size
[InlineData(16384)]  // less typical disk sector and page size
[InlineData(65536)]  // typical texture and buffer alignment for GPU
[InlineData(262144)] // typical non-temporal chunk alignment