[HLSL] Move resource attributes to resource's handles instead of the class itself

[bogner]

Currently resource attributes sit on the resource class itself, like so:

[[hlsl::resource(...)]]
[[hlsl::resource_class(uav)]]
template <typename T> class RWBuffer {
  // ...
};

We'd like the attributes to be attached to the resource's internal handle instead as we move towards the "intangible" handle type:

template <typename T> class RWBuffer {
  [[hlsl::resource(...)]]
  [[hlsl::resource_class(uav)]]
  __hlsl_resource_t Handle;
};

Note that this is not blocked by the introduction of the intangible handle type - resources already have a void *Handle member, and we can simply attach these attributes there.

AC:

• All of the HLSL resource attributes are attached to the handle
• Diagnostic and backend logic that refers to these attributes continues to work
• Existing tests are updated to conform to this approach
• Utility functions added to find information about resource types based on these attributes

[damyanp]

@bob80905 - this may be worth doing before implementing the diagnostics?