internal/zstd: enforce block size limit according to RFC 8878

[aimuz]

This change updates the zstd reader implementation to check for block
size limits as specified by the zstd specification RFC 3.1.1.2.4.
Now, it ensures that both decompressed and compressed sizes of any block
do not exceed the frame's Block_Maximum_Size.

The previous logic only checked the buffer and literal buffer combined
size against a hard-coded maximum which did not account for varying frame
sizes or match lengths. This has been corrected to dynamically calculate
the size based on actual literals and matches processed, ensuring
compliance with the standard.

Updates #63824

[aimuz]

wait #64056

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[gopherbot]

This PR (HEAD: 727183e) has been imported to Gerrit for code review.

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[gopherbot]

Message from Aimuz me:

Patch Set 2:

(1 comment)

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