Remove SetCode() copy in shader instrumentation

[spencer-lunarg]

We have this code

// TODO - This makes a copy, but could save on Chassis stack instead (then remove function from VUL).
// The core issue is we always use std::vector<uint32_t> but Safe Struct manages its own version of the pCode
// memory. It would be much harder to change everything from std::vector and instead to adjust Safe Struct to not
// double-free the memory on us. If making any changes, we have to consider a case where the user inlines the
// fragment shader, but use a normal VkShaderModule in the vertex shader.
modified_shader_module_ci->SetCode(instrumented_spirv);

What is needed is a way in VUL to allow the safe struct to let us manage the memory