Non-cryptographic hash for cache key

[masaori335]

We found that OpenSSL's md5 is expensive (#8719). Replacing the library is an approach, but I start wondering we really need a cryptographic hash here.

#8755 is a PoC of using non-cryptographic hash for URL hash. If we look at collision ratio and benchmarks, the xxhash looks good for this use case.

• https://github.com/Cyan4973/xxHash/wiki/Collision-ratio-comparison
• https://github.com/Cyan4973/xxHash/wiki/Performance-comparison

A concern is when we change the hash algorithm, the cache needs to be cleared once.

[github-actions]

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