Clamp benchmark ranks to respect MaxRank

[Doordashcon]

resolves #7517

Issues

1. Compile-Time vs Runtime Rank Mismatch

• promote_fast Benchmark uses mock runtime's MaxRank during benchmark generation while allowing runtime overrides. Creating potential parameter mismatch between benchmark metadata(i.e. generated r values) and runtime configuration(i.e. T::MaxRank).

2. Static Rank Assumptions

• bump_demote Benchmark initialized members at rank 2, making it incompatible with MaxRank=1 configurations
• promote Benchmark contained hardcoded rank values (1 → 2) which fails for MaxRank=1

Changes

Dynamic Rank Clamping

// promote_fast
let target_rank = r.min(T::MaxRank::get()).try_into().unwrap();

// promote
let to_rank = (current_rank + 1).min(max_rank.try_into().unwrap());