* add merge SSZ consensus object tests
* add merge attestations, attester slashing, proposer slashing, and voluntary exit test fixtures
* throw catchable exception rather than assert on invalid SingleMemberUnion selector
* hash_tree_root can assert, because it's trusted data by that point
* re-assert on writing, since also trusted data
* beta.4 update
* implement upgrade_to_merge()
* add random tests and rename "Official" to "Ethereum Foundation"
* checkDir = true covers dirExists(...)
* invalidate CI EF fixtures cache
* more correct cache invalidation
* initial 0.11.1 spec commit; no test regressions and finalizes in eth2_network_simulation
* with BLS 0.10/0.11 available, stop skipping attester slashing, proposer slashing, and voluntary exist operations fixture tests
* switch param orders to group state.{fork, genesis_validators_root}; bump spec/datatypes spec version for network purposes
* mark attestation construction and broadcast and some minimal/mainnet constants as 0.11.1-compatible; remove phase 1 sharding constants from minimal which don't exist in that preset
tersec
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