Add basic support for replaying from SPIR-V

[Pennycook]

Description of Changes

Previously, replay checked for either an OpenCL C source file (kernel.cl) or a device binary (*.bin). This commit adds another check for a SPIR-V binary (kernel.spv).

The intent behind these changes is to make it simpler to capture on one device and replay on another device, without needing access to the original source. More sophisticated changes would be required to fully automate this and support all cases (e.g., multiple SPIR-V files) but this simple change seemed in keeping with the existing "kernel.cl" path and is enough for my use-case.

Testing Done

I only ran a very simple test:

1. Used OpenCL Intercept Layer to capture a kernel running on an Intel GPU, producing a DeviceBinary0.bin file.
2. Used readelf and dd to extract the .spv section from DeviceBinary0.bin into kernel.spv.
3. Used the modified run.py script to replay the kernel on an Intel CPU via PoCL.

[bashbaug]

Works for me! I think we should be able to dump the .spv file directly, assuming that the program is created from IL, which is probably is in many cases where we are currently dumping the device binary instead. I'll work on this shortly.