Cardano Updates

2468: Replace `hardfork_at` with `eras` object, and add node_era 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.

Content edits to resolve #189

  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"
    }
}
```

<!-- Additional comments or screenshots to attach if any -->

<!--
Don't forget to:

 ✓ Self-review your changes to make sure nothing unexpected slipped through
 ✓ Assign yourself to the PR
 ✓ Assign one or several reviewer(s)
 ✓ Jira will detect and link to this PR once created, but you can also link this PR in the description of the corresponding ticket
 ✓ Acknowledge any changes required to the Wiki
 ✓ Finally, in the PR description delete any empty sections and all text commented in <!--, so that this text does not appear in merge commit messages.
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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.