RaptorCast: Round up chunk assignment

[xinyuan-dev]

This PR implements the rounding up chunk assignment algorithm proposed in #2215.

[Copilot]

Pull Request Overview

This PR implements a rounding-up chunk assignment algorithm for RaptorCast by introducing the StakeBasedWithRC assigner for validator-based RaptorCast. The changes transition from the Partitioned assigner to StakeBasedWithRC for validator RaptorCast while maintaining backward compatibility for full-node RaptorCast.

Key changes:

• Switches validator RaptorCast to use StakeBasedWithRC assigner instead of Partitioned
• Adds comprehensive tests comparing chunk assignment properties between the two assigners
• Updates test infrastructure with more realistic stake distribution modeling

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
monad-raptorcast/src/packet/builder.rs	Updates BuildTarget::Raptorcast to use StakeBasedWithRC assigner
monad-raptorcast/src/packet/assigner.rs	Marks Partitioned::from_validator_set as unused in production, removes unused annotation from StakeBasedWithRC, adds property tests and realistic stake distribution
monad-raptorcast/Cargo.toml	Adds rand_distr dependency for stake distribution modeling
.github/workflows/test-command.yml	Pins cargo-binstall to v1.15.7
.github/workflows/rust.yml	Pins cargo-binstall to v1.15.7

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