scripts: Roundup strings sizes in struct to multiple of 4
scripts: Roundup strings sizes in struct to multiple of 4

vktrace layer needs strings sizes to be multiple of 4 for
data alignment in the trace file.

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools