* extend light client protocol for Electra
Add missing Electra support for light client protocol:
- https://github.com/ethereum/consensus-specs/pull/3811
Tested against PR consensus-spec-tests, the test runner automatically
picks up the new tests once available.
* workaround `version-2-0`: `Error: cannot instantiate: 'SomeUnsignedInt'`
* fix initialization when Electra not scheduled
* try reduce stack size in test
* put correct sync committee branch version into DB
* adjust fork schedule in light client data tests
* further reduce stack size
* split function into multiple parts
* rename variable
* regenerate test reports to cover new Electra tests
* add Nim bug reference
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