Get rid of XXH3 as a dependency by replacing the key used by the hashmap in Metal.

[DarioSamo]

Proposed key instead.

struct ClearPipelineKey {
    uint64_t value = 0;

    union {
       uint64_t depthClear : 1;
       uint64_t msaaCount : 4;
       uint64_t colorFormat0 : 7;
       uint64_t colorFormat1 : 7;
       uint64_t colorFormat2 : 7;
       uint64_t colorFormat3 : 7;
       uint64_t colorFormat4 : 7;
       uint64_t colorFormat5 : 7;
       uint64_t colorFormat6 : 7;
       uint64_t depthFormat : 7;
    }
};