[std]: Use XXHash32 instead FNV-1a

[MaxGraey]

XXHash32 has better quality and speed (especially for 32-bit, 64-bit and >= 16 bytes keys).

FNV-1a:

• Poor uniform distribution. Only up to 14 bits can be used for the hash table (up to 2 ^ 14 hash table slots) without degradation
• Bad avalanche effect
• Speed: 4.5 cyclers per byte

XXHash:

• Excellent uniform distribution
• Near-perfect avalanche effect
• Speed: ~1.7 cyclers per byte

string perf tests

u64 hash tests

old u64 hash (fnv-1a): 281.68000001460314 ms
new u64 hash (xxhash): 189.05499996617436 ms

• I've read the contributing guidelines

[dcodeIO]

🎉