Benchmark derived task scheduling weight function (on development)

[4meta5]

Closes #1138

big improvement on accuracy and maintainability of weights returned in tasks on-initialize wherein task scheduling happens

this is the same as #1139 but it is done and ready for review, the other PR is on top of broken benchmarks for now

[4meta5]

do not return Weight from this inner function

would be better to return the number of tasks actually assigned to the shard (to be added to num_tasks_assigned accumulator below)

[4meta5]

cc @penumbra23 @dvc94ch CI error is:

Run ./timechain-node benchmark pallet --chain development --pallet pallet_networks --extrinsic '*' --output ./weights/networks.rs
2024-09-21 02:44:35 Using the chain spec instead of the runtime to generate the genesis state is deprecated. Please remove the `--chain`/`--dev`/`--local` argument, point `--runtime` to your runtime blob and set `--genesis-builder=runtime`. This warning may become a hard error any time after December 2024.    
Error: Input("The runtime returned an error when trying to build the genesis storage. Please ensure that all pallets define a genesis config that can be built. This can be tested with: [https://github.com/paritytech/polkadot-sdk/pull/3412\nError:](https://github.com/paritytech/polkadot-sdk/pull/3412/nError:) wasm call error Other: Exported method GenesisBuilder_get_preset is not found")

[4meta5]

We are doing v2