:open_umbrella: Small benchmarking issues

[ggwpez]

Some follow-ups from https://github.com/paritytech/substrate/pull/11091:

• [x] Polkadot integration https://github.com/paritytech/polkadot/pull/5137
• [x] Add a minimal test https://github.com/paritytech/polkadot/pull/5137
• [ ] For the overhead sub-command:
  • [x] Add a --header flag analogous to the pallet sub-command to support any file-header #12204
  • [ ] Also put the executor name into the template, since #11170 made wasm default.
  • [ ] Save all results as JSON for further analysis, with split up into mandatory/operational weight
  • [ ] Add --block-weight-key flag with default 26aa394eea5630e07c48ae0c9558cef734abf5cb34d6244378cddbf18e849d96
  • [ ] optional: Some convenience flags such as from and to can be negative to go into the past from the best block.
• [ ] Check whether for_keys_with_prefix needs to use add_read_key

This is a good issue for external contributors.
Should be done after https://github.com/paritytech/substrate/issues/11140

[kziemianek]

@ggwpez the related issue is done. Can I take this?

[ggwpez]

Yea sure @kziemianek! Someone else also wanted to work on it, but I did not hear back from them.
@yourarj or @omadoyeabraham please tell us if you are working on this. Would re-assign it otherwise.

[omadoyeabraham]

@ggwpez I'm working on this.

[omadoyeabraham]

@ggwpez I have a draft PR for this here: https://github.com/paritytech/substrate/pull/11893

But I need clarity on results to save to JSON, and also where/how the --block-weight-key should be utilized