Cardano Updates

  There's really nothing simpler between 'TokenB' compared to 'TokenC', or between '1111111111111111111111111' compared to '22222222222222222222222'

  The goal of a shrinker is to provide smaller counter examples, if shrinking a value doesn't make it smaller, the shrinker is pointless. In this very case, the shrinkers are actually sucking of CPU time for nothing as noted by the 'validateGenerators' property sometimes failing to shrink large data structures in a reasonable time.

  However, allowing values to shrink down to one common denominator help to make a counter example more readable by reducing the amount of noise in an output. That is, it's easier if all values of a particular types are the same. Thus, this commit changes shrinkers to reach that common denominator much more aggressively (in one step).

2468: Replace `hardfork_at` with `eras` object r=Anviking a=Anviking

# Issue Number

ADP-676


# Overview

<!-- Detail in a few bullet points the work accomplished in this PR -->

- [x] Replace `hardfork_at` with info of all eras
- [x] Instead of storing ProtocolParameters in DB, just keep them in a `TVar`
- [ ] <s>See if we can order the eras correctly in the `era` object (for when the JSON is viewed by humans)</s> Seems impossible to do.
- [x] TODO: Extend swagger
- [ ] Tiny doc tweaks

# Comments

- Could add absolute `slot` field also
- Arguably a bit sad that the eras get sorted seemingly alphabetically in the json

```json
$ cardano-wallet network parameters
{
    "slot_length": {
        "quantity": 1,
        "unit": "second"
    },
    "decentralization_level": {
        "quantity": 74,
        "unit": "percent"
    },
    "genesis_block_hash": "5f20df933584822601f9e3f8c024eb5eb252fe8cefb24d1317dc3d432e940ebb",
    "blockchain_start_time": "2017-09-23T21:44:51Z",
    "desired_pool_number": 500,
    "epoch_length": {
        "quantity": 432000,
        "unit": "slot"
    },
    "eras": {
        "shelley": {
            "epoch_start_time": "2020-07-29T21:44:51Z",
            "epoch_number": 208
        },
        "mary": null,
        "byron": {
            "epoch_start_time": "2017-09-23T21:44:51Z",
            "epoch_number": 0
        },
        "allegra": {
            "epoch_start_time": "2020-12-16T21:44:51Z",
            "epoch_number": 236
        }
    },
    "active_slot_coefficient": {
        "quantity": 5,
        "unit": "percent"
    },
    "security_parameter": {
        "quantity": 2160,
        "unit": "block"
    },
    "minimum_utxo_value": {
        "quantity": 1000000,
        "unit": "lovelace"
    }
}
```

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Co-authored-by: Johannes Lund <[email protected]>

We never want to use the old genesis parameters just because the wallet
just started.

The onTipUpdate will be run immediately on startup, and will fetch
both interpreter, and protocol parameters.

To be safe, and for readability, let's replace the TVar+initial val with
an empty TMVar though.

Use relative path of cnode.sh instead of hard coded default
Only match against port to get cnode PID

Co-authored-by: Ola <[email protected]>