Explore Custom Benchmarking Config Trait

[naijauser]

Description

This PR explores the use of a custom Benchmarking Config Trait that houses Benchmarking helpers based on @bkchr 's suggestion in #162. It's an attempt to replace the existing approach that uses a type in the pallet Config.

Inside benchmarking.rs

pub trait BenchmarkConfig: pallet::Config {
	type Helper: BenchmarkHelper<Self>;
}

pub trait BenchmarkHelper<T: Config> {
	fn initialize_and_get_id() -> u32;
}

impl<T: Config> BenchmarkHelper<T> for () {
	fn initialize_and_get_id() -> u32 {
	    ...
	}
}

#[benchmarks(where T: BenchmarkConfig)]
mod benchmarks {
    ...
}

Inside the Runtime lib.rs

impl pallet_example_custom_benchmarking_config::benchmarking::BenchmarkConfig for Runtime {
	type Helper = ();
}

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