[FRAME core] Refactor pallet benchmarking

[ggwpez]

The pallet benchmarking backend and measuring code is rotting away since three years and it becomes increasingly difficult to maintain.
Some medium-large scale refactoring of the involved code in the near future is a good idea IMHO. This would also allow for easier addition of new features and bug-fixing of existing ones.

[vivekvpandya]

@ggwpez could you please create small chunks of refactoring work? I would like to work on them but I don't know much to figure out myself.

[ggwpez]

@vivekvpandya this is a pretty big issue that I would like to either tackle myself or have another dev that is familiar with the code do. There is not much to split up - the code needs a complete face lift.

You can search for mentor issues, these are easier for external devs.
But thanks for asking, many people just start without asking 😅

[eskimor]

One important aspect in my opinion: Either make sure to always measure the case where all parameters are 0 or otherwise ensure that the base case won't get over estimated. This is currently a blocker for getting proper weights for backed candidates.