Emit a resolvable type name for Runtime Async continuations in GC heap dumps

[tommcdon]

The GCHeapDump BulkType event set fixedSizedData.TypeNameID = TypeHandle::GetCl() and the type name from TypeHandle::GetName(). For a metadata-less Runtime Async continuation MethodTable, GetCl() is the nil TypeDef token (0x02000000) and GetName() yields an empty string, so eventpipe readers such as dotnet-gcdump render every continuation as
Type(0x02000000) with no usable name.

Describe continuations using the base Continuation type (via UpCastTypeIfNeeded) for the module id, name token, and name, while keeping the per-object TypeID as the derived MethodTable so GCBulkNode entries still resolve to this record. This
also avoids MethodTable::GetModule()'s IsContinuationWithoutMetadata() assert on
checked builds.

Validated with dotnet-gcdump against a process holding 128 live continuations:

• Baseline: 128 objects showed as Type(0x02000000)
• Fix: they show as System.Runtime.CompilerServices.Continuation and the capture still succeeds.

Adds a test case for runtime-async to cover this scenario.

Relates to #120800

[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.

[dotnet-policy-service]

Tagging subscribers to this area: @steveisok, @tommcdon, @dotnet/dotnet-diag
See info in area-owners.md if you want to be subscribed.

[Copilot]

Pull request overview

This PR updates CoreCLR GC heap dump type emission so runtime-async metadata-less continuation subtypes are reported with a resolvable, non-empty type name (by using an upcast “named” TypeHandle for module/token/name), and adds an EventPipe regression test to cover the scenario.

Changes:

• Adjust GCHeapDump BulkType logging to use TypeHandle::UpCastTypeIfNeeded() for ModuleID, TypeNameID, and the emitted type name, while keeping TypeID as the actual object MethodTable.
• Add a new EventPipe test app that creates suspended runtime-async continuations and validates that BulkType entries never have an empty TypeName.
• Add a dedicated csproj configuring the feature flag and runtime-async enablement for the test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/coreclr/vm/eventtrace_bulktype.cpp	Emits module/token/name using an upcast type for metadata-less runtime-async continuation subtypes.
src/tests/tracing/eventpipe/gcdump_runtimeasync/gcdump_runtimeasync.csproj	New test project enabling runtime-async=on and setting DOTNET_RuntimeAsync=1.
src/tests/tracing/eventpipe/gcdump_runtimeasync/gcdump_runtimeasync.cs	New regression test that captures a GC heap snapshot and asserts type names are non-empty (and continuation types appear).

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/tests/tracing/eventpipe/gcdump_runtimeasync/gcdump_runtimeasync.csproj:10

• The comment says runtime-async is enabled via an AppContext switch set in Main, but the test doesn't set any AppContext switch. The only runtime enablement here appears to be the DOTNET_RuntimeAsync test environment variable below, so the comment is misleading.

    <!-- Emit Runtime Async method bodies so the runtime creates the dynamic metadata-less
         continuation MethodTables this test exercises. The runtime side is enabled in-process
         via the AppContext switch set in Main. -->
    <Features>$(Features);runtime-async=on</Features>

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/tests/tracing/eventpipe/gcdump_runtimeasync/gcdump_runtimeasync.cs:72

• This runtime-async guard makes the test silently pass (return 100) if runtime-async isn’t actually enabled, which can make the test vacuous and hide regressions. It also risks a NullReferenceException if reflection ever fails to locate the method. Prefer treating this as a hard failure (or use attribute-based skip logic) and avoid the possible null dereference.

            // Verify Runtime Async is actually active; otherwise the test would be vacuous.
            var mi = typeof(GCDumpRuntimeAsyncTest).GetMethod(nameof(Suspended),
                System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
            bool runtimeAsync = (mi.MethodImplementationFlags & System.Reflection.MethodImplAttributes.Async) != 0;
            if (!runtimeAsync)