Fix chunk is padding circuit

[zhenfeizhang]

Description

#670 (comment)

First of all, the is_smaller_than rely on some assumption that both operands are small, but both the num_of_valid_chunks and value are private cells.

num_of_valid_chunks is a public input https://github.com/scroll-tech/zkevm-circuits/blob/static-proof-aggregation/aggregator/src/aggregation/circuit.rs#L380-L386
rlc_config.load_private(region, &Fr::from(i as u64), offset)?; missed a copy constraint from fixed column. should have loaded a constant 1 and accumulate from there. will fix

this is the fix

Issue Link

[link issue here]

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Contents

• fix soundness bug in chunk_is_valid function

Rationale

[design decisions and extended information]

How Has This Been Tested?

[explanation]

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[zhenfeizhang]

closed as integrated to #712