Add per-descriptor-set IO mapping shift values.

This PR adds the ability to provide per-descriptor-set IO mapping shift
values.  If a particular binding does not land into a per-set value,
then it falls back to the prior behavior (global shifts per resource class).

Because there were already 6 copies of many different methods and internal
variables and functions, and this PR would have added 6 more, a new API is
introduced to cut down on replication and present a cleaner interface.
For the global (non-set-specific) API, the old entry points still exist
for backward compatibility, but are phrased internally in terms of the
following.

    // Resource type for IO resolver
    enum TResourceType {
        EResSampler,
        EResTexture,
        EResImage,
        EResUbo,
        EResSsbo,
        EResUav,
        EResCount
    };

Methods on TShader:

    void setShiftBinding(TResourceType res, unsigned int base);
    void setShiftBindingForSet(TResourceType res, unsigned int set, unsigned int base);

The first method replaces the 6 prior entry points of various spellings, which
exist now in depreciated form.  The second provides per-resource-set functionality.
Both accept an enum from the list above.

From the command line, the existing options can accept either a single shift value as
before, or a series of 1 or more [set offset] pairs.  Both can be provided, as in:

    ... --stb 20 --stb 2 25 3 30 ...

which will use the offset 20 for anything except descriptor set 2 (which uses 25) and
3 (which uses 30).

Test/hlsl.shift.per-set.frag

@@ -0,0 +1,59 @@
+// Test register class offsets for different resource types
+
+SamplerState       s1 : register(s1, space1);
+SamplerComparisonState s2 : register(s2, space2);
+
+Texture1D <float4> t1 : register(t1, space1);
+Texture2D <float4> t2 : register(t2, space1);
+Texture3D <float4> t3 : register(t1, space2);
+
+StructuredBuffer<float4> t4 : register(t1, space3);
+
+ByteAddressBuffer t5 : register(t2, space3);
+Buffer<float4> t6 : register(t3, space3);
+
+RWTexture1D <float4> u1 : register(u1, space1);
+RWTexture2D <float4> u2 : register(u2, space2);
+RWTexture3D <float4> u3 : register(u3, space2);
+
+RWBuffer <float> u4 : register(u4, space1);
+RWByteAddressBuffer u5 : register(u4, space2);
+RWStructuredBuffer<float> u6 : register(u4, space3);
+AppendStructuredBuffer<float> u7 : register(u4, space4);
+ConsumeStructuredBuffer<float> u8 : register(u4, space5);
+
+cbuffer cb : register(b1, space6) {
+    int cb1;
+};
+
+tbuffer tb : register(t7) {
+    int tb1;
+};
+
+float4 main() : SV_Target0
+{
+    t1;
+    t2;
+    t3;
+    t4[0];
+    t5.Load(0);
+    t6;
+
+    s1;
+    s2;
+
+    u1;
+    u2;
+    u3;
+
+    u4[0];
+    u5.Load(0);
+    u6[0];
+    u7;
+    u8;
+
+    cb1;
+    tb1;
+
+    return 0;
+}