[SM6.9] Support long vector declaration, casting, and assignment

[pow2clk]

Long vectors should be supported in

• Elements of arrays, structs, StructuredBuffers, and ByteAddressBuffers.
• Parameters and return types of non-entry functions.
• Stored in groupshared memory.
• Static global variables.
• Local function scoped variables.

This task is to allow declaring vectors of size greater than 4 using the template declaration in all of the above. In addition, they should be assignable, initializable, and castable in ways consistent with existing vectors using splatted scalars, initializer lists, constructors, and casted arrays. The best way to test this is probably a library shader since that allows exporting non-entry functions which allows parameters to be used to verify the assignment operations.

Some example assignments:

vector<uint, 5> InitList = {1, 2, 3, 4, 5};
vector<uint, 6> Construct = vector<uint, 6>(6, 7, 8, 9, 0, 0);
uint4 initval = {0, 0, 0, 0};
vector<uint, 8> VecVec = {uint2(coord.xy), vecB};
vector<uint, 6> Assigned = vecB;
float arr[5];
vector<float, 5> CastArr = (vector<float, 5>)arr;
vector<float, 6> ArrScal = {arr, 7.9};
vector<float, 10> ArrArr = {arr, arr};
vector<float, 15> Scal = 4.2;