SSZ errors `OffsetSkipsVariableBytes(NNNN)` on all electra spec-test

[rodrigo-o]

After the initial configuration of the electra-support branch, all spec test fail with the same error OffsetSkipsVariableBytes(NNNN), before starting tackling them one by one we need to get rid of the common issues, in this case this is related to the old schema for Containers, we need to update our container implementation with the changes introduced in electra.

[rodrigo-o]

Closed in #1400