Shaders: replace timeinfo (x+w)/30 with z

[sprunk]

There's a pattern in shaders where things use (timeInfo.x + timeInfo.w) / 30 to get non-discrete game time. This is confusing and mistake-prone. Replace such patterns with timeInfo.z.

Note that timeInfo.z was added in 105-2366 so it's ideal to wait a bit until we are sure the engine won't be reverted earlier than that.