Cardano Updates

This was resolving an issue where (likely for another reason), rapidly
submitted transactions required re-enqeueing of ReqTx inputs.

Hypothesis: When the input queue was not bounded, another bounded
queue (in Hydra.Logging) was creating delays leading to the re-enqeued
retrying of applying transactions start to fail (because they time out).

It is not known why the chain of transactions we used (see hydra-cluster
bench) was even requiring the re-enqeuing in the first place though.

Improves logging throughput by combining 64KB block buffering with batch
draining of the `TBQueue`.

Benchmark (LOG_N=100000, --time-limit 10) shows buffered+batched ~196 ms
vs flush-each ~543 ms (~2.8× faster). This keeps log output format and
monitoring behavior unchanged, but logs may appear in bursts and have
slightly higher latency.

If we exclude batching the win is ~1.28x 

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<!-- 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

> when calculating the slot drift

* extended NodeSynced and NodeUnsynced with time and slot drifts
* added Haddocks to both currentSlot and currentChainTime
* made NodeState.currentChainTime non optional
* defined initialChainTime = posixSecondsToUTCTime 0

> NodeState now tracks currentChainPoint :: ChainPointType tx, instead of currentSlot :: ChainSlot + currentChainTime :: Maybe UTCTime
> NodeSynced and NodeUnsynced now carry ChainPointType tx, instead of chainTime :: UTCTime
> extended IsChainState class with chainPointTime :: ChainPointType tx -> UTCTime
> initialChainTime = posixSecondsToUTCTime 0

This reverts commit 037aea1d9f15f65db00113f0606f9e09d0b03548.

This reverts commit 037aea1d9f15f65db00113f0606f9e09d0b03548.

> NodeState now tracks currentChainPoint :: ChainPointType tx, instead of currentSlot :: ChainSlot + currentChainTime :: Maybe UTCTime
> NodeSynced and NodeUnsynced now carry ChainPointType tx, instead of chainTime :: UTCTime
> extended IsChainState class with chainPointTime :: ChainPointType tx -> UTCTime
> initialChainTime = posixSecondsToUTCTime 0