chore(snowflake): add more randomness in server id fallback

[Altahrim]

Summary

CRC32 hash function can easily lead to collisions when based on hostname (and even using random strings).

Here is an example which generates a lot of duplicated server IDs from different fake hostnames:

for ($i = 1; $i <= 20; ++$i) {
	$a=sprintf('prod-%02d.nextcloud.com', $i); 
	printf("%s xxh: %3d crc:%3d\n", $a, hexdec(hash('xxh32', $a)) % 512, crc32($a) %512); 
}

prod-01.nextcloud.com xxh: 182 crc:265
prod-02.nextcloud.com xxh: 280 crc:368
prod-03.nextcloud.com xxh: 116 crc:152
prod-04.nextcloud.com xxh: 348 crc:386
prod-05.nextcloud.com xxh: 171 crc:106
prod-06.nextcloud.com xxh: 452 crc: 19
prod-07.nextcloud.com xxh:  71 crc:507
prod-08.nextcloud.com xxh: 292 crc:102
prod-09.nextcloud.com xxh: 363 crc:398
prod-10.nextcloud.com xxh:  68 crc:368
prod-11.nextcloud.com xxh: 406 crc:152
prod-12.nextcloud.com xxh: 213 crc:225
prod-13.nextcloud.com xxh: 179 crc:265
prod-14.nextcloud.com xxh:  64 crc: 19
prod-15.nextcloud.com xxh: 210 crc:507
prod-16.nextcloud.com xxh:  47 crc:386
prod-17.nextcloud.com xxh: 175 crc:106
prod-18.nextcloud.com xxh: 383 crc:503
prod-19.nextcloud.com xxh: 222 crc: 31
prod-20.nextcloud.com xxh: 274 crc:386

With $a=bin2hex(random_bytes(10)); I also spotted one collision with CRC32.

Even if it's only used as a fallback, XXH32 sounds like a better alternative.

Performance
XXH32 should be faster but we need to convert to int:

Summary
  php -r 'for ($a=0;$a<10000;++$a) { crc32($a); }' ran
    1.07 ± 0.15 times faster than php -r 'for ($a=0;$a<10000;++$a) { echo hexdec(hash("xxh32", $a)); }'
    1.11 ± 0.17 times faster than php -r 'for ($a=0;$a<10000;++$a) { echo bindec(hash("xxh32", $a, true)); }'

It's quite close :)

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[Altahrim]

/backport to stable34

[Altahrim]

/backport to stable33