feat(security): add configurable IPv6 subnet for BFP and throttling

[Altahrim]

• Follow-up of feat(ip): use larger IPv6 range by default #52015

Summary

Allows to configure subnet size for IPv6 normalization and use smaller default.

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)

[Altahrim]

/backport to stable31

[Altahrim]

/backport to stable30

[Altahrim]

/backport to stable29

[provokateurin]

LGTM, just the comment needs adjustment

[come-nc]

This broke on 32bit: https://github.com/nextcloud/server/actions/runs/14584944718/job/40908705961

There were 4 errors:

1) Test\Security\Normalizer\IpAddressTest::testGetSubnet with data set #5 ('2001:0db8:0000:0000:0000:8a2e...0:7334', '2001:db8::/56')
ValueError: 64-bit format codes are not available for 32-bit versions of PHP

/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:44
/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:85
/__w/server/server/tests/lib/Security/Normalizer/IpAddressTest.php:64

2) Test\Security\Normalizer\IpAddressTest::testGetSubnet with data set #6 ('2001:db8:3333:4444:5555:6666:7777:8888', '2001:db8:3333:4400::/56')
ValueError: 64-bit format codes are not available for 32-bit versions of PHP

/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:44
/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:85
/__w/server/server/tests/lib/Security/Normalizer/IpAddressTest.php:64

3) Test\Security\Normalizer\IpAddressTest::testGetSubnet with data set #7 ('::1234:5678', '::/56')
ValueError: 64-bit format codes are not available for 32-bit versions of PHP

/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:44
/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:85
/__w/server/server/tests/lib/Security/Normalizer/IpAddressTest.php:64

4) Test\Security\Normalizer\IpAddressTest::testGetSubnet with data set #8 ('[::1]', '::/56')
ValueError: 64-bit format codes are not available for 32-bit versions of PHP

/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:44
/__w/server/server/lib/private/Security/Normalizer/IpAddress.php:85
/__w/server/server/tests/lib/Security/Normalizer/IpAddressTest.php:64

I suppose those tests can simply be skipped on 32bits?
@Altahrim

[susnux]

Fix in #52392

P cannot be used on 32bit you need to use VV (possible as we set it to 0 anyways).