* update get_seed(...) and get_beacon_proposer_index(...) to 0.9.0, implement compute_proposer_index(...), and render 3 more test fixtures working
* rm stray Crosslink reference which prevented static SSZ tests from building
* remove references to removed tests in attestations test fixture; add minimal-preset block sanity test, plus all but one of mainnet tests for block sanity to transition fixtures
* transition deposit operations fixture to 0.9.0
* mark slash_validator(...) as 0.9.0
* switch remaining non-ref objects to ref objects to maybe avoid crashes in CI
* remove unused helpers/debug_state imports
* enable all sanity slots tests
* enable more tests in sanity blocks
* win64 strikes again #435
* workaround invalid handle in win64 CI
* empty_epoch_transition_not_finalizing only valid in minimal preset
* sanity block ETH1 data votes are also minimal only
* Add sanity check for slot processing (also impacted by https://github.com/status-im/nim-beacon-chain/issues/373)
* use reportDiff also for all state tests vs EF
* initial sanity checks for blocks - workaround zero signature in block headers: https://github.com/status-im/nim-beacon-chain/issues/374
* Remove generic object variant compare commented code
* Add the one block state transition sanity checks
* generalize blocks test to multiple blocks
* simplify slots test runner
* Add official epoch transitions, sanity blocks, sanity slots to the test suite
* Fix index out-of-bounds in initiate_validator_exit - enable proposer slashings unittest