[mono][aot] Fix recursive struct wrapper normalization

[pavelsavara]

Summary

Reintroduces the Mono AOT wrapper-normalization fix from #135029 after its
revert in #135371, with a corrected regression test.

mono-aot-cross recursively normalizes value-type fields and generic type
arguments when it builds gsharedvt wrapper signatures. A valid type such as:

struct GenericFieldBox<T>
{
    public object Value;
}

struct SelfRecursive
{
    public GenericFieldBox<SelfRecursive> Value;
}

makes get_wrapper_shared_vtype() and get_wrapper_shared_type_full() call
each other until the native stack overflows.

The fix carries a stack-allocated chain of value types currently being
normalized. Re-entering a type, or reaching the bounded depth for a generic
shape that grows at every level, uses the existing "keep the original type"
fallback.

What changed since #135029

The original product fix was not the source of the cross-platform CI failures.
The original test also declared mutually recursive generic value types:

struct A { GenericFieldBox<B> Value; }
struct B { GenericFieldBox<A> Value; }

CoreCLR rejects that metadata with TypeLoadException while loading
System.Runtime.Tests, before xUnit test discovery. This caused #135348 on
WASI, Firefox, Android, and iOS.

This PR removes that invalid mutual shape. The test uses only the valid
self-recursive shape that reproduces the Mono AOT compiler failure. Its helper
types are private.

Validation

• .\build.cmd -bl -os browser -subset mono+libs -c Debug /p:RuntimeFlavor=Mono
  • Passed, 0 warnings/errors.
• Preserved reverted-main mono-aot-cross compiling the exact modified
  System.Runtime.Tests.dll
  • Failed with 0xC00000FD native stack overflow, as expected.
• Patched mono-aot-cross compiling the same assembly
  • Passed; 28,452/29,246 methods compiled.
• Mono browser interpreter, Chrome:
  System.Tests.ValueTypeTests
  • Passed, 23/23; XHarness exit 0.
• Clean Release Mono/browser build in a separate worktree
  • Passed, 0 warnings/errors.
• Mono browser AOT, Chrome:
  System.Tests.ValueTypeTests
  • AOT-compiled 80 assemblies; passed 23/23; XHarness exit 0.
• Original source-only Blazor reproduction from Blazor WASM AOT Compilation Failure #132071:
  • App assembly passed (109/110 methods compiled).
  • Dedup aot-instances.dll passed (14,712/14,747 methods compiled).
• Standalone CoreCLR metadata probes:
  • Self-recursive generic field loads successfully.
  • Removed mutual-recursive shape throws the same TypeLoadException reported
    by [ci-scan] Test failure: System.Runtime.Tests TypeLoadException for StructWithMutualGenericFieldA #135348.

Resolves #132071

Note

This PR description was drafted with GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.