Non-cryptographic hash for cache key

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.