vkd3d-shader/hlsl: Rename hlsl_reg.bind_count to hlsl_reg.allocation_size.

We have to distinguish between the "bind count" and the "allocation size"
of variables.

The "allocation size" affects the starting register id for the resource to
be allocated next, while the "bind count" is determined by the last field
actually used. The former may be larger than the latter.

What we are currently calling hlsl_reg.bind_count is actually the
"allocation size", so a rename is in order.

The real "bind count", which will be introduced in following patches,
is important because it is what should be shown in the RDEF table and
some resource allocation rules depend on it.

For instance, for this shader:

    texture2D texs[3];
    texture2D tex;

    float4 main() : sv_target
    {
        return texs[0].Load(int3(0, 0, 0)) + tex.Load(int3(0, 0, 0));
    }

the variable "texs" has a "bind count" of 1, but an "allocation size" of
3:

    // Resource Bindings:
    //
    // Name                                 Type  Format         Dim      HLSL Bind  Count
    // ------------------------------ ---------- ------- ----------- -------------- ------
    // texs                              texture  float4          2d             t0      1
    // tex                               texture  float4          2d             t3      1

libs/vkd3d-shader/hlsl.h

@@ -257,7 +257,7 @@ struct hlsl_reg
     /* Number of registers to be allocated.
      * Unlike the variable's type's regsize, it is not expressed in register components, but rather
      *  in whole registers, and may depend on which components are used within the shader. */
-    uint32_t bind_count;
+    uint32_t allocation_size;
     /* For numeric registers, a writemask can be provided to indicate the reservation of only some
      *   of the 4 components. */
     unsigned int writemask;