[stable26] fix unencrypted_size for folders when scanning the filesystem with encryption enabled

[backportbot-nextcloud[bot]]

• [x] :warning: This backport had conflicts that were resolved with the 'ours' merge strategy and is likely incomplete

backport of #36857

[blizzz]

Psalm complaints:

Error: lib/private/Files/Cache/Cache.php:899:13: InvalidReturnType: The declared return type 'int' for OC\Files\Cache\Cache::calculateFolderSizeInner is incorrect, got 'float|int' (see https://psalm.dev/011)
Error: lib/private/Files/Cache/Cache.php:977:10: InvalidReturnStatement: The inferred type 'float|int' does not match the declared return type 'int' for OC\Files\Cache\Cache::calculateFolderSizeInner (see https://psalm.dev/128)
Error: lib/private/Memcache/APCu.php:66:16: InvalidClass: Class, interface or enum APCUIterator has wrong casing (see https://psalm.dev/007)

[blizzz]

moving to 26.0.4

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moving to 26.0.5

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moving to 26.0.6

If there are no updates in any form until building 26.0.6, I will close this PR.

[blizzz]

→ 26.0.7