Constant wgpu_core::pipeline_cache::HASH_SPACE_VALUE

const HASH_SPACE_VALUE: u64 = 0xFEDCBA9_876543210;

The value used to fill PipelineCacheHeader::hash_space

If we receive reports of pipeline cache data corruption which is not otherwise caught on a real device, it would be worth modifying this

Note that wgpu does not protect against malicious writes to e.g. a file used to store a pipeline cache. That is the resonsibility of the end application, such as by using a private space.