Proposals for second iteration of the HFC

The most intricate parts of the HFC related to how time/era transitions are performed have been largely unmodified since they were first introduced[^1]. Recently, investigating https://github.com/input-output-hk/cardano-ledger/issues/3491 lead us to scrutinize these aspects, resulting in improving our understanding of the status quo and giving rise to potential improvements.

As the aforementioned issue has been resolved in https://github.com/input-output-hk/ouroboros-consensus/pull/366 (albeit in a relatively ad-hoc fashion), there is no immediate need to make any large HFC changes. Instead, the purpose of this issue is to give an overview over the HFC-related changes that came out of this effort.

### Documentation

- [x] There is now a [HWW entry for the status quo of the HFC](https://input-output-hk.github.io/ouroboros-consensus/docs/for-developers/HardWonWisdom#the-hard-fork-combinator-interface).
- [ ] https://github.com/IntersectMBO/ouroboros-consensus/issues/921

### HFC behavior

- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/345
- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/416
- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/417
- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/413 (likely part of implementing alternatives to block counting)
- "Block counting" related:
- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/385
- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/389 (might supersede the previous point)
- [ ] https://github.com/input-output-hk/ouroboros-consensus/issues/419

### HFC implementation/testing

- [ ] https://github.com/IntersectMBO/ouroboros-consensus/issues/1336

[^1]: This is largely due to the fact that they did their job well, with one notable exception: https://github.com/input-output-hk/ouroboros-network/pull/3754