refactor: params.ChainConfigExtra & RulesExtra -> params/extras

[darioush]

Moves the ChainConfigExtra type to a new package which doesn't register libevm type configurations.

[qdm12]

Good job 👍

All my comments are on a small things to change in existing code that got simply moved to params/extras, but which shows as "new code" by git (git doesn't detect the file movement); I prefixed these comments with OOS/part-of-new-git-deltas: to highlight I'm aware this is not new new code.

How is our team feeling about this: are we ok to improve/fix small things when we have code showing as new git additions, despite it being out of scope with the PR (as long as it's not geth specific code)? I personally find this as a good way to improve code/comments occasionally, especially since we will likely not focus on reviewing all the code otherwise, but happy to not do this in the future if we feel it hurts us more than it helps us.