[Feature Request] Debugger API to create ref structs

ICorDebug has various ICorDebugEval APIs to create value types, but ref structs have a requirement that they be placed in stack memory. Visual Studio would like to run func-evals that take the addresses of ref structs as arguments (for example `System.Private.CoreLib.dll!System.Runtime.CompilerServices.DefaultInterpolatedStringHandler..ctor(int literalLength, int formattedCount)`) but they need to be able to create the ref struct first. Currently there is no ICorDebug API that can allocate types on the stack.