Similar to the existing `RewardInfo`, this PR adds the infrastructure
needed to export epoch processing information from altair+. Because
accounting is done somewhat differently, the PR uses a fork-specific
object to extrct the information in order to make the cost on the spec
side low.
* RewardInfo -> EpochInfo, ForkedEpochInfo
* use array for computing new sync committee
* avoid repeated total active balance computations in block processing
* simplify proposer index check
* simplify epoch transition tests
* pre-compute base increment and reuse in epoch processing, and a few
other small optimizations
This PR introduces the type and does the heavy lifting in terms of
refactoring - the tools that use the accounting will need separate PR:s
(as well as refinements to the exportred information)
f90b2b8b1f