Metal: Use setBytes:length:atIndex for arguments
Metal: Use setBytes:length:atIndex for arguments

Instead of allocating a temporary MTLBuffer, if the arguments
size is less than 4KB, use setBytes:length:atIndex.  See
https://developer.apple.com/reference/metal/mtlcomputecommandencoder/1443159-setbytes?language=objc#discussion
for more information.

Former-commit-id: 7e31506b03785b1f65fa1b2f64c98db9a30fec68
darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide