Add cbor round trip tests for Block for each era

[teodanciu]

Description

While looking into roundtrip tests, I discovered we don't have any for Block.

I have added such tests for each era to cardano-protocol-tpraos.
Since Block is defined in core, the tests would be better suited in core, and then referenced and ran in each, but the problem is the reference to BHeader which is defined in cardano-protocol-tpraos.
Is there something else I can use instead of BHeader ? I can see there is BHeaderView, but it doesn't seem to be suitable for this kind of testing.

Another note: the cddlRoundTrip specs don't pass for Block, because of the checks we make in the TxSeq DecCBOR instances - the data we're generating from cddl is not internally consistent to pass these checks.

Checklist

• Commits in meaningful sequence and with useful messages
• Tests added or updated when needed
• CHANGELOG.md files updated for packages with externally visible changes
  
  New section is never added with the code changes. (See RELEASING.md)
• Versions updated in .cabal and CHANGELOG.md files when necessary, according to the
  versioning process.
• Version bounds in .cabal files updated when necessary
  
  If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• Code formatted (use scripts/fourmolize.sh)
• Cabal files formatted (use scripts/cabal-format.sh)
• hie.yaml updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[lehins]

It is better to add this funciton to the testlib, so it can be used in consensus as well. For this it needs to be parameterized by block header

Suggested change

	roundTripBlock ::
	forall era.
	( EraSegWits era
	, Arbitrary (Tx era)
	) =>
	Spec
	roundTripBlock =
	prop (show (typeRep $ Proxy @(Block (BHeader StandardCrypto) era))) $
	withMaxSuccess 3 $
	roundTripAnnEraExpectation @era @(Block (BHeader StandardCrypto) era)
	roundTripBlock ::
	forall era bh.
	( EraSegWits era
	, Arbitrary (Tx era)
	) =>
	Spec
	roundTripBlock =
	prop (show (typeRep $ Proxy @(Block bh era))) $
	withMaxSuccess 3 $
	roundTripAnnEraExpectation @era @(Block bh era)

[teodanciu]

Sure! good point, thanks.

[lehins]

These do not make sense, because block header as defined in this package is never used with Babbage onwards

Suggested change

	roundTripBlock @BabbageEra
	roundTripBlock @ConwayEra

[teodanciu]

Yeah I wondered about whether it brings any value at all like this, but I agree, no point testing unrealistic stuff.
I will try adding for TxSeq instead!