[GENX]: Enhance operator `genx.matrix.dpas` to allow more input shapes

The `genx.matrix.dpas` operator is lowered to a SIMT DPAS instruction. The operands of the DPAS instructions (A,B) have several constraints, depending on the data type of the vector element. These are the expected input operands shapes:

1. If the size of the element is 16 bits (`f16`, `bf16`): the expected input A, B operands' types are `vector<8 x f16>` or `vector<8 x bf16>`, the GENX translation generates a bitcast to `vector<8 x i16>` to satisfy IGC's requirements

2. If the size of the element is 32 bits (`tf32`): the expected input A, B operands types are `vector<4 x tf32>`, i.e., half of the row or column, the GENX translation generates a bitcast to `vector<4 x i32>`

3. If the size of element is 8 bits (`i8`, `u8`): the expected input A, B operands types are `vector<8 x i16/u16>`, i.e. 2 adjacent elements of i8/u8 are packed into a 16 bit element type

For case (1) there are no issues while for case (2) and (3) the operator requirements cause the producer to pack data before creating the operation, specifically:

- case 2: if the producer input types (for A, B) are `vector<8 x tf32>` it needs to *split* it to two `vector<4 x tf32>` between two SIMD lanes/Warp elements before calling the GENX operation.

- case 3: if the produces input types (for A, B) are `vector<16 x i8/u8>` it needs to *pack* the two adjacent 8 bit elements into a `vector<8 x i16/u16>` before calling the GENX operation

The `genx.matrix.dpas` operator should be improved to allow inputs of type `vector<8 x tf32>` (case 2) and `vector<16 x i8/u8>` (case 3). The operation should take care of packing or splitting the input vectors appropriately.