* opencl: refactor initialization
* opencl: refactor GPU identification
* opencl: rename for consistency
* opencl: cache global mem size in dev_ctx
* opencl: adjust log level
* opencl: load argsort and flash_attn kernels in supports_op
* argsort kernel must be built for supports_op for querying the max
workgroups
* flash_attn kernel has many variants, only load them when needed