[runtime tests] Make 5 tests conditional on multithreading support

[radekdoulik]

Note

This PR description was generated with the help of GitHub Copilot.

Disable tests that call Thread.Start() on single-threaded platforms (e.g., browser WASM) by using ConditionalFact with PlatformDetection.IsMultithreadingSupported.

These tests unconditionally create and start new threads, which fails on single-threaded WASM where Thread.Start() is not supported.

Tests changed

• finally_SEH (baseservices/exceptions) — spawns thread in finally block
• rethrow (baseservices/exceptions) — spawns threads for exception rethrow testing
• Polyrec (Loader/regressions) — spawns 4 threads for polymorphic recursion
• test1 (Loader/TypeInitialization/backpatching) — spawns threads for static constructor race
• InterlockExchange (Regressions) — spawns 99 threads for interlocked ops

Changes

• [Fact] → [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsMultithreadingSupported))]
• Added using TestLibrary; and <ProjectReference Include="$(TestLibraryProjectPath)" /> where not already present

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[Copilot]

Pull request overview

This PR aims to avoid failures on single-threaded platforms (e.g., browser WASM) by skipping a small set of tests that unconditionally call Thread.Start(). In addition, the PR includes CoreCLR VM changes related to portable entrypoints/interpreter behavior and interpreter frame allocation alignment.

Changes:

• Convert 5 thread-spawning tests from [Fact] to [ConditionalFact(...IsMultithreadingSupported)] and add TestLibrary references where needed.
• Add $(TestLibraryProjectPath) project references to affected test projects.
• Update CoreCLR VM interpreter/portable-entrypoint logic and adjust interpreter frame allocation to use aligned allocation.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/tests/Regressions/coreclr/1514/interlockexchange.cs	Skip thread-heavy regression test when multithreading isn’t supported.
src/tests/Loader/regressions/polyrec/Polyrec.csproj	Add TestLibrary project reference for PlatformDetection usage.
src/tests/Loader/regressions/polyrec/polyrec.cs	Gate polymorphic recursion multithreaded test behind multithreading support.
src/tests/Loader/classloader/TypeInitialization/backpatching/test1.cs	Skip type-init race test on single-threaded platforms.
src/tests/baseservices/exceptions/regressions/V1/SEH/COOL/rethrow.csproj	Add TestLibrary project reference for PlatformDetection usage.
src/tests/baseservices/exceptions/regressions/V1/SEH/COOL/rethrow.cs	Gate thread-based rethrow test behind multithreading support.
src/tests/baseservices/exceptions/regressions/V1/SEH/COOL/finally.cs	Gate thread-based finally/SEH regression test behind multithreading support.
src/tests/baseservices/exceptions/regressions/V1/SEH/COOL/finally_SEH.csproj	Add TestLibrary project reference for PlatformDetection usage.
src/coreclr/vm/method.cpp	Adjust ShouldCallPrestub entrypoint selection for MethodImpl/.override + portable entrypoints.
src/coreclr/vm/interpframeallocator.cpp	Use aligned allocation/free and align interpreter allocations to INTERP_STACK_ALIGNMENT.
src/coreclr/vm/interpexec.cpp	Add interpreter code-prep fallback for MethodImpl/.override vtable-slot remapping scenarios.