The templates for `BeaconBlock`, `BeaconBlockBody` and `BeaconState`
are the only ones using a `macro` mechanism for code generation.
This prevents using the dot-syntax style `consensusFork.BeaconFoo`
in some situations, and also tends to trigger naming conflicts,
requiring the `Type` suffix. Furthermore, the `macro` only works
for types that are re-defined in every single `ConsensusFork`.
Replacing with the simpler but more verbose approach used for other
types for consistency and to avoid the downsides of the `macro`.
Furthermore, simplify `test_fixture_sanity_blocks` to use `forks` sugar.
dd1f362536