Cardano Updates

Refactor such that each example from an era is build on top of the
example of the previous era.

Allows:
* reduced duplication
* each example of each era has most fields set with values

Update block and tx cbor golden files given changes in the block and
transation content.

From https://github.com/IntersectMBO/cardano-api at 229dcd4d8668582167e33b64c2b437261e7e6655

docs(pathway): Session 12 Cardano Developer Pathway diagram and diagram UX

If the release-candidate branch was not merged back to master
after a release, the cabal files will have the wrong version.
The sed replacement will silently match nothing, and the release
will ship binaries with a stale version string.

Detect this upfront and fail with a clear error message telling
the operator to merge the RC branch back first.

docs(pathway): Session 12 Cardano Developer Pathway diagram and diagram UX

The release-candidate script derived OLD_CABAL_VERSION from the
latest git tag, but the cabal files can drift from the tag (e.g.
v2026-03-31 shipped with cabal version 0.2025.12.15). This caused
sed to find no matches, leaving the cabal files unbumped and the
release binary reporting the wrong version.

Read the version directly from cardano-wallet.cabal instead.