#8314 left a few ugly potentially panicking location behind - all of them believed to be unreachable, but this PR fixes them regardless for good hygiene.
Update to `ethereum_ssz 0.10.4` for two new helpers: `not_inplace` and `clone_zeroed`.
Remove remaining `expect` and `todo!` in favour of these helpers and one new fallible (but practically infallible) method.
Co-Authored-By: Daniel Knopik <daniel@dknopik.de>