add SPIR-V testing for integer dot products

[bashbaug]

This PR adds testing for integer dot products via SPIR-V rather than via OpenCL C. The overall logic for this test largely follows the same testing logic as the test_integer_ops test.

The test checks SPIR-V modules using both the SPV_KHR_integer_dot_product extension (works with any SPIR-V version) and SPIR-V 1.6, without the SPV_KHR_integer_dot_product extension.

[bashbaug]

Note: The majority of the changes are all of the different permutations of SPIR-V files:

• There are two different combinations of SPIR-V files that are supported: SPV_KHR_integer_dot_product and SPIR-V 1.6.
• There are three different type combinations that are supported: U, S, and SU.
• There are two different opcodes that are tested: OpXDot and OpXDotAccSat.
• There are two different operand types that are supported: 4 x 8-bit vectors and packed 32-bit integers.
• There are two different bit widths that are supported: 64-bit and 32-bit.

Right now, each permutation is in a separate file, so there are a total of 2 x 3 x 2 x 2 x 2 = 48 different SPIR-V files.

I want a separate kernel for each test scenario, but I can try to consolidate similar variants into the same file, if desired. Is this worthwhile?