Handling of locally scoped resources references

[bogner]

Resources can be declared in function scope, assigned to each other, passed to functions, and put in local arrays.

RWBuffer<float> Buf;

[numthreads(1,1,1)]
void main() {
    RWBuffer<float> T = Buf;
    T[0] = 0;
}

This tracks handling of the various behaviours this entails.

• [HLSL] Design of constructors for resource handle initialization #209
• operator= for resource classes
• Handling of resource assignment through control flow and optimization barriers

[hekota]

Closing this as we won't be using umbrella tasks like this going forward.