refactor(memoryinfo): use ini_parse_quantity for memory limit parsing

[joshtrichards]

• Resolves: #

Summary

Refactor MemoryInfo to leverage PHP's (8.2+) native ini_parse_quantity() for parsing and converting memory_limit values.

• Eliminates custom logic and unnecessary checks.
• Fully aligns parsing with PHP's internal parsing behavior.
• Fixes a bug where our support for float in this particular context was too generous, because on 32-bit systems PHP's own parsing of this value wraps. By switching to this new function we are literally checking from PHP's perspective rather than checking the user's intent. Checking actual effective config value is more appropriate in this context.

Refactor Util::uploadLimit(), maxUploadFilesize(), and related helpers to improve reliability, correctness, and standards alignment.

• Use PHP's native ini_parse_quantity() for accurate parsing of upload_max_filesize and post_max_size, replacing custom logic and computerFileSize().
• Normalize both 0 and -1 as unlimited for INI settings, consistently returning -1 instead of INF or 0 for unlimited upload settings.
• Throw InvalidArgumentException for invalid or unparsable INI values, making misconfigs fail fast instead of silently.
• Always return the stricter of upload_max_filesize or post_max_size, with clear logic and optional warning on misconfiguration.
• Update maxUploadFilesize() logic to clearly and robustly combine quota/free space and system limits, supporting unlimited semantics correctly.
• Improve docblocks for clarity and standards compliance.
• Remove ambiguous or legacy code paths, reducing edge cases and future bugs.

Refs:

• https://www.php.net/manual/en/function.ini-parse-quantity.php
• https://php.watch/versions/8.2/ini_parse_quantity#:~:text=Version8.2,string%20$shorthand):%20int%20%7B%20%7D

TODO

• Make similar changes to Util::uploadLimit()

  • server/lib/public/Util.php

    Line 564 in 3f9849d

    public static function uploadLimit(): int|float {

• Make similar changes in ServerInfo
  • https://github.com/nextcloud/serverinfo/blob/dd28d4025f2facb672695cb90e99cfeea3f12adf/lib/PhpStatistics.php#L27
• Look for other similar spots

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)