[wasi][R2R] unreachable trap in SocketAsyncEventArgs.DnsConnectAsync state machine #134948

Description

With CoreCLR WASI ReadyToRun, System.Net.Sockets.Tests crashes with wasm trap: wasm unreachable instruction executed inside R2R code for SocketAsyncEventArgs.DnsConnectAsync:

wasm trap: wasm `unreachable` instruction executed
    0: corerun!System_Net_Sockets_System_Net_Sockets_SocketAsyncEventArgs___DnsConnectAsync_g__Core_113_0_d__MoveNext
    1: corerun!WasmDelayLoadHelper->EagerImports->SignaturePointer_ReadyToRunHelper_DelayLoad_MethodCall(Kind:DelayLoadHelper,Sig:vTp)
    2: corerun!S_P_CoreLib_System_Runtime_CompilerServices_AsyncMethodBuilderCore__Start<...DnsConnectAsync...>
    ...

The last test started was System.Net.Sockets.Tests.SocketTaskExtensionsTest.EnsureMethodsAreCallable. An unreachable in compiled code usually comes from a JIT-side not-yet-implemented path. The compilation options include JitWasmNyiToR2RUnsupported, which should reject such methods rather than emit a trap. Look at the wasm for this MoveNext to find the trapping construct.

Seen in trimmed ReadyToRun runs of the CoreCLR WASI library tests for #134813. The non-R2R CI lane also fails this suite; its signature has not been compared yet.