Limit pre allocation in cbor decoding (ZKP-45)

[DOBEN]

Purpose

https://linear.app/concordium/issue/ZKP-45/rust-cbor-decoding-vulnerability

Changes

• Memory pre allocation is capped to MAX_PRE_ALLOCATED_SIZE=4096 when cbor decoding vectors and maps.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

CLA acceptance

_Remove if not applicable.

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• link: https://developers.concordium.com/CLAs/Contributor-License-Agreement-v1.0.pdf

• I accept the above linked CLA.