Cardano Updates

Added in order to be able to apply some function on the `txAuxData`
field of a transaction even when the `txAuxData` field is set to
`SNothing`.

Add Test.Cardano.Ledger.Api.State.Query.Examples to the api testlib.

Relax header protocol version for testnets

This check that was introduced for the protocol version in the block header
proved to be problematic for testnets. Which makes sense, since it was
designed for mainnet in mind and its introduction was needed to be done
urgently since it was blocking 10.6.2 release. See #5595 for more context

In order to allow for testnets to continue being able to produce blocks
for older protocol versions with latest version of the node we lift this
restriction, but only for any network with `Testnet` network id. This is
implemented as a temporary measure and will be properly fixed in
Dijkstra era. See #5763 for more context

* Verification of `PrevGovActionId` in `proposalsAddAction` happens on
  accumulated `proposals`
* While `preceedingHardFork` check happens on original `st`.

In a usual application, which has identifiers assigned, this inconsistency
would have been a problem. However, in a transaction's `GovActionId`, which is
derived from a hash of a transaction itself, it is impossible to reference
a previous governance action within the same transaction, since one would need
to know the hash of a transaction that contains the proposal it tries to
reference.

Therefore, this commit fixes not an issue, but a mere inconsistency.
This is done in order to avoid developers even considering this edge case.

Remove redudant import

Add Test.Cardano.Ledger.Api.State.Query.Examples to the api testlib.

This check that was introduced for the protocol version in the block header
proved to be problematic for testnets. Which makes sense, since it was
designed for mainnet in mind and its introduction was needed to be done
urgently since it was blocking 10.6.2 release. See #5595 for more context

In order to allow for testnets to continue being able to produce blocks
for older protocol versions with latest version of the node we lift this
restriction, but only for any network with `Testnet` network id. This is
implemented as a temporary measure and will be properly fixed in
Dijkstra era. See #5763 for more context

* Verification of `PrevGovActionId` in `proposalsAddAction` happens on
  accumulated `proposals`
* While `preceedingHardFork` check happens on original `st`.

In a usual application, which has identifiers assigned, this inconsistency
would have been a problem. However, in a transaction's `GovActionId`, which is
derived from a hash of a transaction itself, it is impossible to reference
a previous governance action within the same transaction, since one would need
to know the hash of a transaction that contains the proposal it tries to
reference.

Therefore, this commit fixes not an issue, but a mere inconsistency.
This is done in order to avoid developers even considering this edge case.

* Verification of `PrevGovActionId` in `proposalsAddAction` happens on
  accumulated `proposals`
* While `preceedingHardFork` check happens on original `st`.

In a usual application, which has identifiers assigned, this inconsistency
would be a problem. However, in a transaction`GovActionId` is derived from
a hash of a transaction itself. This means that it is impossible to reference
a previous governance action within the same transaction, since you'd need to
know a hash of a transaction that contains the proposal itself.

Therefore, this commit fixes not an issue, but a mere inconsistency.
This is done in order to avoid developers even considering this edge case.