v4.0.4-rc.0

Ignore some untimely attestations (#12387)

* Ignore some untimely attestations

* correct child slot check

* consider tips as viable for checkpoints

* deal with canonical blocks

* forkchoice unit tests

* blockchain readonly beacon state

* Ignore some untimely attestations

* correct child slot check

* consider tips as viable for checkpoints

* deal with canonical blocks

* forkchoice unit tests

* blockchain readonly beacon state

* Fix AttestationTargetState mock

* Fix ineffectual assignment lint

* Fix blockchain tests

* Fix build

* Add Nil check

* add comment on lock

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Co-authored-by: terence tsao <terence@prysmaticlabs.com>
Co-authored-by: Preston Van Loon <pvanloon@offchainlabs.com>