Cardano Updates

We encountered a limit of maximum messages we can submit through the
etcd-backed network layer (2MB) when we had scenarios with expensive to
validate or just lots of transactions queuing up. This led to very big
snapshots which eventually hit that limit.

Limiting the number of transactions in a snapshot effectively results in
a bounded block size for the Hydra L2. It must not be configurable or it
becomes a protocol parameter.

This could be related / a root cause to the symptoms we see in #2422 and
similar recent performance problems. Also #2431 should have exposed more
of this because validation is just so much more expensive with big utxo
sets. Besides this, #2442 might be sensible thing to do anyways (Indeed,
both together improve the behavior a lot)

---

<!-- Consider each and tick it off one way or the other -->
* [x] CHANGELOG updated or not needed
* [ ] Documentation updated or not needed
* [ ] Haddocks updated or not needed
* [ ] No new TODOs introduced or explained herafter

<!-- Describe your change here -->

Closes https://github.com/cardano-scaling/hydra/issues/2449

---

<!-- Consider each and tick it off one way or the other -->
* [X] CHANGELOG updated or not needed
* [X] Documentation updated or not needed
* [X] Haddocks updated or not needed
* [X] No new TODOs introduced or explained herafter

Moved from hydra-node library to the hydra-node:testlib component.
    
Instances and generators that were in eg `Hydra.X.Y.Z` in
`hydra-node/src` are now in a module named `Test.Hydra.X.Y.Z` located in
`hydra-node/testlib`.

Also needed to fix knock on effects in other packages.

Addresses https://github.com/cardano-scaling/hydra/issues/2394

---

<!-- Consider each and tick it off one way or the other -->
* [x] CHANGELOG updated or not needed
* [x] Documentation updated or not needed
* [x] Haddocks updated or not needed
* [x] No new TODOs introduced or explained herafter

Moved from hydra-node library to the hydra-node:testlib
component.

Instances and generators that were in eg `Hydra.X.Y.Z` in
`hydra-node/src` are now in a module named `Test.Hydra.X.Y.Z`
located in `hydra-node/testlib`.

Moved from hydra-node library to the hydra-node:testlib
component.

Instances and generators that were in eg `Hydra.X.Y.Z` in
`hydra-node/src` are now in a module named `Test.Hydra.X.Y.Z`
located in `hydra-node/testlib`.

Moved from hydra-node library to the hydra-node:testlib
component.

Instances and generators that were in eg `Hydra.X.Y.Z` in
`hydra-node/src` are now in a module named `Test.Hydra.X.Y.Z`
located in `hydra-node/testlib`.

Moved from hydra-node library to the hydra-node:testlib
component.

Instances and generators that were in eg `Hydra.X.Y.Z` in
`hydra-node/src` are now in a module named `Test.Hydra.X.Y.Z`
located in `hydra-node/testlib`.