RemoteExecutor field marshaling failure when in Live Unit Testing

### Summary 

55 unit tests in the [dotnet/maintenance-packages](https://github.com/dotnet/maintenance-packages) repo that try to use `RemoteExecutor` are failing due to unsupported field marshaling when attempting to run them with Live Unit Testing.

Note that all the unit tests pass without any issues in all other contexts:
- When running them with regular Text Explorer.
- When executed via CLI using `dotnet test`.
- When executed in the CI (rolling builds or PRs).

@dotnet/interop-contrib @dotnet/runtime-infrastructure 

### Repro steps

1. Open the solution using the `build.cmd -vs MaintenancePackages.sln` command.
2. Test menu -> Live Unit Testing -> Start. If asked, choose a location for the `lut` folder. Wait for the tests to finish.
3. Go to the Live Unit Testing tab. Select any of the failing tests. The callstack will look something like this:

```
 System.Buffers.ArrayPool.Tests.ArrayPoolUnitTests.RentBufferFiresRentedDiagnosticEvent

  Message: 
System.ArgumentException : Field marshaling is not supported by Invoke: CS$InstrumentationPayload1

  Stack Trace: 
RemoteExecutor.GetMethodInfo(Delegate d) line 596
RemoteExecutor.Invoke(Action method, RemoteInvokeOptions options) line 118
ArrayPoolTest.RemoteInvokeWithTrimming(Action method, Int32 timeout) line 48
ArrayPoolUnitTests.RentBufferFiresRentedDiagnosticEvent() line 403
```

The exception is being thrown in line 596: 
https://github.com/dotnet/arcade/blob/162990f9a2002aba463bea29e4db1d416cf9d5fd/src/Microsoft.DotNet.RemoteExecutor/src/RemoteExecutor.cs#L578-L596


	private static MethodInfo GetMethodInfo(Delegate d)
	{
	// RemoteInvoke doesn't support marshaling state on classes associated with
	// the delegate supplied (often a display class of a lambda). If such fields
	// are used, odd errors result, e.g. NullReferenceExceptions during the remote
	// execution. Try to ward off the common cases by proactively failing early
	// if it looks like such fields are needed.
	if (d.Target != null)
	{
	// The only fields on the type should be compiler-defined (any fields of the compiler's own
	// making generally include '<' and '>', as those are invalid in C# source). Note that this logic
	// may need to be revised in the future as the compiler changes, as this relies on the specifics of
	// actually how the compiler handles lifted fields for lambdas.
	Type targetType = d.Target.GetType();
	foreach (var fi in targetType.GetFields(BindingFlags.Public \| BindingFlags.NonPublic \| BindingFlags.Instance \| BindingFlags.DeclaredOnly))
	{
	if (fi.Name.IndexOf('<') == -1)
	{
	throw new ArgumentException($"Field marshaling is not supported by {nameof(Invoke)}: {fi.Name}");

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RemoteExecutor field marshaling failure when in Live Unit Testing #14634

carlossanlop
openedon Mar 21, 2024

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